• Account Notifications

    Account Notifications are timely, relevant, and personalized messages sent by companies to their customers about their accounts.

  • Ad Exchange

    An Ad Exchange is a digital marketplace where advertisers and publishers can buy and sell display, video, and mobile advertising.

  • Ad Impression

    An Ad Impression occurs when an advertisement is displayed on a web page.

  • Ad Unit

    An Ad Unit is the web page container that holds the advertising copy and graphics for a digital advertisement.

  • Affiliate Marketing

    Affiliate Marketing is an activity in which companies offer to pay individuals or other businesses — the ‘affiliates’ — to promote their products or services, usually in return for a commission on any sales made.

  • Ahoy

    Ahoy, a signal word originally used to call a ship, was once a standard way to greet others and was Alexander Graham Bell’s suggested greeting for answering the telephone.

  • Allow List

    An Allow List is a set of email or IP addresses that have been granted access to to a service, or a list of web sites that a user is permitted to access.

  • Alphanumeric Sender ID

    An Alphanumeric Sender ID is your company name or brand used as the Sender ID in one-way SMS messages sent to supported countries. Alphanumeric Sender IDs may be up to 11 characters long. Accepted characters include both upper- and lower-case Ascii letters, the digits 0 through 9, and the space character. They may not be only numerals.

  • API

    An Application Programming Interface (API) is provided by a service owner so that others may use the features and functions enabled by the service. APIs describe how a consumer will make requests of the servuce, and what they will receive in return.

  • API Key

    An Application Programming Interface (API) Key is a unique identifier that is used to authenticate a developer or program to an API.

  • Application

    An Application, often shortened to ‘app’, is a program, or set of programs, that allows end-users to perform particular functions. For example, ecommerce companies provide applications to customers to facilitate purchases and service.

  • Application-to-Person Messaging

    Application-to-Person messaging (A2P) is any kind of message traffic in which a person is receiving messages from an application rather than another individual, and which is not expected to receive a reply. A2P message includes, but is not limited to, marketing communications, appointment reminders, chat bots, notifications, and one-time passwords (OTPs) or PIN codes.

  • Appointment Reminder

    An Appointment Reminder is a message sent by a business to notify a customers of an upcoming event, such as an eye test, a restaurant booking or a package delivery. While some businesses call customers to remind them of their appointments, text messaging has emerged as the preferred channel for this kind of communication.

  • Area Code Overlay

    An Area Code Overlay is an area code that covers the same geographical space as another area code. In North America, each area code has a potential capacity of around 8 million unique phone numbers — 7,919,900, to be exact. Many area codes have exhausted all possible phone numbers, so one or more area codes are added to accommodate.

  • A Record

    An A Record — more accurately, a ‘DNS A Record’ — links a domain to an IP address.

  • Arrival Alerts

    An Arrival Alert is sent by a business to inform one of its customers when they might expect their product or service to arrive.

  • Artificial Intelligence

    Artificial Intelligence (AI) is the ability of a computer to mimic human cognitive skills, such as learning and understanding.

  • Attribute-Based Routing

    Attribute-Based Routing is a process used by contact center applications to distribute tasks according to a set of defined characteristics.

  • Automated Email

    Automated Email allows you to dynamically send relevant content to individual recipients.
  • Autoresponder

    Autoresponders generate email responses to actions and events.
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  • Basic Authentication

    Basic Authentication is a method for an HTTP user agent (e.g., a web browser) to provide a username and password when making a request.

  • Bayesian Filter

    Bayesian Filtering is a technique for detecting spam.
  • Blocks

    Blocked emails happen when your IP address has been added to a deny list or has been blocked by an ISP or messaging organization.
  • Bounces

    Bounced emails are emails that are returned to the server that sent them.

  • Bulk Email Service

    Bulk email service is a way to send an email, or multiple emails, to a large list of various recipients.
  • Bulk Mail Folder

    Bulk Mail folder is also called “spam” or “junk” folder, the folder where questionable email is routed.
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  • C#

    C# — pronounced “see sharp” — is an object-oriented and statically typed computer programming language created by Microsoft for use on its .NET platform. Its name comes from the C language, from which it inherits a similar syntax.

  • Call Attribution

    Call Attribution is a way to track calls by tying phone numbers to data from an ad source, such as keywords, sessions or campaigns. It provides visibility into digital campaigns and allows accurate measurement of marketing return on investment (RoI).

  • Call Center

    A call center is the heart of customer service for many businesses, where customers call in for help and reps call out for sales. It’s referred to as a “call center” because traditional models of customer service are based on phone support as the main method of contact between customers and companies. A modern call center is often referred to as a contact center.

  • Call Routing

    Call routing refers to the procedure of sending voice calls to a specific queue based on predetermined criteria. A call routing system is also known as an automatic call distributor (ACD).

  • Call Tracking

    Call Tracking is a software-based performance marketing technique that generates and assigns a unique phone number to a specific advertisement or marketing campaign. Call Tracking systems then follow and analyze leads through that phone number “channel” to understand the channel’s true effectiveness and ROI or receive a commission for driving that lead.

  • Call Transcription

    Call transcription is the conversion of a voice or video call audio track into written words to be stored as plain text in a conversational language. Call transcription can either be live - as a call or event happens - or based on the recording of a past conversation.

  • Call whisper

    Call Whisper, also commonly referred to as Call Screening, involves playing a message to the callee while the caller continues to hear ringing. It can provide additional information such as the source or purpose of the call to the callee before the call begins and even allow the callee to accept or reject the call based on that information.

  • Campaigns

    Campaigns are used to send custom emails to targeted recipient segments.

    The CAN-SPAM Act lists the guidelines, requirements, and penalties regarding the sending of commercial bulk email.
  • Categories

    Paying attention to your deliverability metrics can help optimize your delivery rate and reduce the risk of being seen as a spammer.
  • Challenge Response

    An automated reply to a sender to filter out spammers.
  • Chatbot

    A chatbot is an artificial intelligence (AI) program that creates conversational interaction between the chatbot and another user through voice commands or text chats.

  • Clicks and Unique Clicks

    Track the links your customers click from your emails with SendGrid.

  • Click-Through Rate (CTR)

    What is CTR?
  • Click-to-Call

    Click-to-call, sometimes called click-to-talk or click-to-dial, is a way to let people connect with a company representative by phone while they’re browsing a website or in an app.

  • Cloud Contact Center

    Cloud contact centers make contact center software functionality that was previously only accessible through on-premise hardware available through the internet. A cloud contact center provides quick and easy access to the tools and services businesses need to communicate in today’s web-based world.


    The CNAME record creates an alias for subdomain.yourdomain.com and points it to another domain
  • Complaint

    When an email recipient identifies an email message as spam or junk by clicking the “report spam” or “mark as junk” button within their email reader.
  • Contact Center

    A contact center is a business’s central point for managing all customer communications across all channels. A company’s contact center is usually integrated with their customer relationship management (CRM) system, where all interactions between the organization and the public are tracked, coordinated, and managed.

  • CPS

    Calls per second

  • Customer Engagement

    Customer engagement is the emotional connection between your company and your customers, sentiments which strongly influence their buying decisions. Customers who actively engage with a business tend to be more loyal and spend their money supporting brands they feel connected to.

  • Customer Experience

    Customer experience (sometimes abbreviated CX) refers to the interactions between a customer and an organization throughout all points of contact. A good customer experience is strongly correlated with customer loyalty and company revenue growth.

  • Customer Journey

    A customer journey is the total sum of experiences a customer has when interacting with a business or organization. Rather than focusing on a specific interaction, the customer journey takes all points of contact into account.

  • Customer Relationship Management (CRM)

    Customer relationship management, usually referred to as CRM, is a method for managing an organization's relationships with its customers. Most often, the term CRM refers to a CRM system—which is software for managing contacts, streamlining sales processes, and improving business relationships.

  • Customer Satisfaction Score (CSAT)

    Short for Customer Satisfaction Score, CSAT is a measurement to determine whether a customer feels their expectations have been fulfilled by a company’s products and services.

  • Custom Fields

    Custom fields allow you add extra information about your contacts to your contact database.
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  • Deferral

    A deferred status can occur when an ISP or mailbox provider is for some reason not ready to accept email from your IP address.
  • Deliverability

    Email deliverability is a critical component for all email communication with customers. Strong deliverability is a necessity for any web application.
  • Delivery

    A delivery is recorded when a request to send an email results in the delivery of that email to the end recipient.
  • Demand-Side Platform (DSP)

    Definition of a Demand-Side Platform (DSP)
  • Deny list

    A list of IP addresses that are known to send unsolicited or unwanted emails
  • Direct Inward Dialing (DID)

    Direct Inward Dialing (DID) is a telephone service that allows a phone number to ring through directly to a specific phone at a business instead of going to a menu or a queue and needing to dial an extension. A phone number that is used like this is often called a "DID" (and multiple numbers are called "DIDs”).

  • Direct Response Advertising

    Definition of Direct Response Advertising
  • DKIM

    DKIM is an email authentication protocol that helps ISPs better identify legitimate email senders.


    Domain-based Message Authentication, Reporting and Conformance (DMARC) is a standard for determining the authenticity of the person or service sending email on behalf of a domain.
  • DNS

    Domain Name System (DNS) translates a domain name into an IP address to find the owner’s site.
  • Domain

    A named internet address that resolves to an IP address
  • Domain authentication

    Domain authentication shows email providers that SendGrid has your permission to send emails on your behalf.
  • Drip Campaign

    Drip Campaigns are a type of automated email marketing strategy.
  • Drops

    In certain cases, SendGrid will “Drop” a message to a specific email address in order to protect your sender reputation. SendGrid keeps Email Lists to track bounces, spam reports, and unsubscribes for each of our users.
  • DTMF Tones (Dual-Tone Multi-Frequency Tones)

    DTMF, or Dual-Tone Multi-Frequency tones, are in-band telecommunications signals sent over voice frequencies.  Commonly used over telephone lines, DTMF tones are also commonly called Touch Tones.

  • Dynamic Number Insertion (DNI)

    Dynamic Number Insertion (DNI) is a call tracking feature where a unique phone number is tied to each ad source. This helps marketers analyze offline behavior much in the same way they track online behavior with the help of cookies.

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  • E.164

    E.164 is the international telephone numbering plan that ensures each device on the PSTN has globally unique number.

    This number allows phone calls and text messages can be correctly routed to individual phones in different countries. E.164 numbers are formatted [+] [country code] [subscriber number including area code] and can have a maximum of fifteen digits.

  • Email API Integration

    Email API integration allows senders to easily sync their email service provider with their platform and software tools to automate key functions
  • Email Authentication

    Technical standards to help ISPs and other receivers validate the identity of an email sender.
  • Email Harvesting

    Email harvesting is the process of obtaining lists, either by purchase or theft, of valid email addresses for the purpose of sending bulk email or spam
  • Email Marketing

    Email Marketing represent the email communications sent to promote a commercial product or service.
  • Email Service Provider

    An email service provider provides transactional and marketing email services.
  • ETA Alerts

    ETA Alerts, or Estimated Time of Arrival Alerts, are periodic notifications on the status of an item, delivery, or person that include a probable time of arrival at the destination.  Usually delivered through SMS messages or voice calls, ETA alerts keep customers updated on the location and timing of their upcoming deliveries.

  • Event Webhook

    Event Webhooks provides data about the email you send when the user takes an action.
  • Expandable Banner

    Definition of an Expandable Banner
  • Expired

    Bounced - Expired emails are emails that are unable to be delivered within 72 hours.
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  • Feedback Loop

    A feedback loop is the process by which an ISP forwards emails reported as spam for immediate removal by the sender.
  • Flex Dialpad

    The Flex Dialpad is a native feature of the Flex UI v1.18.0 and offers all of the theming and customizability features of a React component.

    Flex Dialpad allows agents to make outbound calls to customers directly from the UI and transfer calls to a supervisor for immediate help. Additionally, it helps supervisors monitor calls, and users run real-time and historical reporting through Flex Insights.

    With the programmable Flex dialpad, developers can build click-to-dial use cases via the new Action Framework action, startOutboundCall. For instance, you can program the dialpad in such a way that Flex retrieves contact data from your business application and subsequently present it to an agent. This kind of automation avoids any possible risk of misdialing and reduces time-to-call by leveraging data that resides in your application. 

  • Flex Insights

    Flex Insights allows you to perform workforce optimization (WFO) in Twilio Flex. It provides a 360-degree view of every conversation in your Flex contact center so that you can provide agents with valuable feedback, knowledge, and skills.

  • Flighting in Advertising

    Definition of Flight or Flighting in Advertising
  • Frequency Capping

    Definition of Frequency Capping
  • Fully Qualified Domain Name (FQDN)

    Definition of a fully qualified domain name as it relates to SendGrid.
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  • General Data Protection Regulation (GDPR)

    The General Data Protection Regulation (GDPR) of the European Union (EU) is a law that regulates the handling of personal data and outlines the rights individuals have with regard to their data. It was implemented on May 25, 2018. It applies to any “individual, company, or organisation” that processes the data of a person in the EU. This applies whether the organization is based in the EU or elsewhere.

  • General Data Protection Regulation (GDPR)

    The General Data Protection Regulation (GDPR) of the European Union (EU) is a law that regulates the handling of personal data and outlines the rights individuals have with regard to their data.
  • General Packet Radio Service (GPRS)

    GPRS, or General Packet Radio Service, is a best-effort packet-switching communications protocol for cellular networks.  

    GPRS was one of the first widely used data transfer protocols on cellular networks, first standardized in 3GPP's Release 97 in the first quarter of 1998.  Commercial cellular networks began to support GPRS in 2000.

  • GSM-7

    GSM-7 is a character encoding standard which packs the most commonly used letters and symbols in many languages into 7 bits each for usage on GSM networks.  As SMS messages are transmitted 140 8-bit octets at a time, GSM-7 encoded SMS messages can carry up to 160 characters.

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  • Header

    An email header is the information that tells email recipients and servers where the email has come from and where it should go.
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  • IMAP

    IMAP is a protocol many applications use to retrieve mail from your mail server
  • Interactive Voice Response (IVR)

    Interactive Voice Response or IVR is an automated telephony system that interacts with human callers through the use of voice and touch-tone keypad selections (DTMF tones). It’s also commonly known as a phone tree.

  • Internet of Things (IoT)

    The Internet of Things (IoT) refers to devices that sense or manipulate some part of the physical world and are connected through the Internet. By virtue of their being networked, these devices can share information and data, and enable new applications and business models.

  • Invalid Email

    occurs when you attempt to send email to an address that is formatted in a manner that does not meet internet email format standards.
  • IP Address

    A unique numerical address that defines an internet location.
  • IP Warmup

    Initially splitting up the email send requests from a new dedicated IP, so it doesn't get blocked.

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  • Jitter

    Jitter is the variation in periodicity of a signal or periodic event from its target or true frequency.  In telecommunications, jitter further refers to the variation in latency of packets carrying voice or video data over a communications channel.

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  • Latency

    Latency is the time delay between the initiation of an event and its perception by some observer.  In networking and telecommunications, latency is the time between a sender causing a change in a system's state and its reception by an observer.  Network latency is often informally used interchangeably with lag.

  • Link branding

    Email link branding allows all of the click-tracked links and opens tracked images in your emails to be from your domain instead of from sendgrid.net.
  • Lists

    Lists are simply static collections of Marketing Campaigns contacts.
  • Live Chat

    Live chat is a type of online chat distinguished by its simplicity and user accessibility. Live chat appears in a web browser or in mobile applications, usually via a small pop-up modal through which the visitor can exchange text messages with a chat operator in real time.

  • Long Code

    A long code number is a standard phone number used to send and receive voice calls and SMS messages. Phone numbers are typically called “long codes” (10-digit numbers in many countries) when comparing them with SMS short codes (5-6 digit numbers).

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  • Machine Learning

    Machine learning is an application of artificial intelligence that enables computer programs to learn and improve automatically as they are exposed to new data, without being explicitly programmed.

  • Mailbox Provider

    An email service provider provides transactional and marketing email services.
  • Mail Merge

    Mail Merge is a process to create customize emails from a generic form or template.

  • Masked Calling

    Masked Calling is a technique used in ecommerce to protect buyers’ and sellers’ personal phone numbers. Each party gets a temporary number, allowing them to communicate for a specified time period. When the time period expires, the numbers are recycled and reassigned to other parties on the platform. This prevents transactions from happening outside the platform. 

  • Masked Phone Numbers

    Masked Phone Numbers are a common pattern to anonymize communication between multiple parties and hide participant phone numbers. Instead of dialing directly from phone to phone, users communicate via a third ('proxy') phone number that forwards a call to the eventual destination. 

  • Mean Opinion Score (MOS)

    A Mean Opinion Score (MOS) is a numerical measure of the human-judged overall quality of an event or experience.  In telecommunications, a Mean Opinion Score is a ranking of the quality of voice and video sessions.

    Most often judged on a scale of 1 (bad) to 5 (excellent), Mean Opinion Scores are the average of a number of other human-scored individual parameters.  Although originally Mean Opinion Scores were derived from surveys of expert observers, today a MOS is often produced by an Objective Measurement Method approximating a human ranking.

  • Microprocessor

    A Microproccessor is an integrated circuit whose function is almost infinitely changeable through programming.

  • MMS

    MMS, short for Multimedia Messaging Service, is a standard way to send multimedia such as pictures, videos, and other attachments over text messaging channels.

  • MTA

    MTA stands for Mail Transfer Agent. It is software that transfers electronic mail messages from one computer to another using a client–server application architecture.
  • Multichannel

    In a multichannel contact center, companies connect with customers via multiple communications channels – such as email, social media, web chat, and voice. However, just because customers connect via multiple channels does not mean that their experience is seamless.

  • MX Record

    An Mail Exchanger Record specified the mail server responsible for accepting email on behalf of a domain
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  • National Format

    Twilio’s Lookup API returns phone numbers in national format, a string containing the phone number formatted according to the most common style in the associated country.

  • Native Advertising

    Definition of Native Advertising
  • Natural Language Processing (NLP)

    Natural language processing (NLP) helps computers understand and interpret human language by breaking down the elemental pieces of speech.

  • Natural Language Understanding (NLU)

    Natural language understanding (NLU) uses the power of machine learning to convert speech to text and analyze its intent during any interaction.

  • Net Promoter Score (NPS)

    Net promoter score, often referred to as NPS, is an important metric that measures how likely customers are to recommend a business. The idea behind NPS is companies who are recommended by their customers are more likely to grow.

  • Network Address Translation (NAT)

    Network Address Translation (NAT) is the modification of in-transit network packets to map one IP address space to another.  It is most commonly used in IP Masquerading, where a large private IP network shares a relatively small number of publicly facing IP addresses behind a router or gateway.

  • Network Edge

    A network edge is a location where a computer network interfaces with the Internet. A network connected to the Internet may have one or more network edges located in data centers throughout the world.

  • North American Area Codes

    North American Area Codes are prefixed to a phone number to assist in routing phone calls in North America. The North American Numbering Plan (NANP) dictates the regional and non-geographic area codes assigned to signatory countries. The United States, Canada, some Caribbean countries, and all US territories are covered by the plan.

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  • Omnichannel

    In an omnichannel contact center, all communication channels (such as phone, SMS, online chat, and email) are connected and integrated to provide a seamless customer experience. Omnichannel contact centers let agents switch between channels from one user interface, without losing context from customer interactions across all other channels.

  • On-Premise Contact Center

    An on-premise contact center is a contact center model where all software and hardware required to maintain and operate a call center is located on a customer’s property. Companies using an on-premise system generally employ or contract with specialized IT staff responsible for configuration, upgrades, and upkeep of the contact center.

  • Open Rate

    The rate in which your customers open emails you've sent to them.
  • Open Relay

    An SMTP server configured in such a way that it allows anyone on the Internet to send email through it.
  • Opens & Unique Opens

    Track how many times your emails are opened with SendGrid
  • Order notifications

    Order notifications give businesses the ability to inform customers of the status of their order, which could include confirmations, pricing adjustments, delays in fulfillment, or delivery scheduling.

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  • P2P SMS

    P2P stands for Person-to-Person messaging. In simple terms, this is when two or more people communicate over text messaging. For example, when you send a text message from your phone to another person's phone, that's P2P. Under some circumstances, this may also include traffic that goes through an API to connect two people, however some countries (including the US and Canada) do not consider any application-mediated traffic to be P2P.

  • Packet Loss

    Packet loss refers to the failure of packets to reach their destination on a network.  Packet loss is most often a consequence of network congestion and usually caused by network equipment dropping, ignoring, misdelivering, or discarding packets.

  • PDD

    Post-dial delay (PDD) is the measurement of how long it takes for a calling party to hear a ringback tone after initiating a call. Technically it is the delta between the SIP INVITE and a 180 Ringing or 183 Session Progress response. 

  • Peer-initiated Invitations Campaign

    Peer-initiated Invitations are a Marketing Email campaign where you get customers to invite their friends and family. There are some caveats to consider about this marketing method.
  • Personally Identifiable Information (PII)

    Personally Identifiable Information (PII), or personal data, is data that corresponds to a single person. PII might be a phone number, national ID number, email address, or any data that can be used, either on its own or with any other information, to contact, identify, or locate a person.

  • Phishing

    A technique for acquiring information such as user names, passwords, credit cards, social security numbers and other personal data by masquerading as a trusted business.
  • Phone Menu

    A phone tree or phone menu is an automated navigation menu presented to voice callers. Using interactive voice response with DTMF codes (touch tones) or voice recognition, a phone menu helps a caller find automated information, complete a transaction, talk to the proper human operator, or leave a voicemail with a company.

  • Platform

    A platform is any combination of hardware and software used as a foundation upon which applications, services, processes, or other technologies are built, hosted, and/or run. Platforms offer the ability to build within an existing technical framework, decreasing both development time and cost.

  • Preheader

    A preheader is the short summary text that follows the subject line when an email is viewed in the inbox. Many mobile, desktop, and web email clients provide them to tip you off on what the email contains before you open it.
  • Private Branch Exchange (PBX)

    PBX, short for Private Branch Exchange, is a phone system in an enterprise that manages incoming and outgoing phone calls as well as an organization’s internal communications.

  • Programmatic Media Buying

    Definition of Programmatic Media Buying
  • PSTN (Public Switched Telephone Network)

    The PSTN (Publicly Switched Telephone Network) is the network that carries your voice calls when you call from a landline or cell phone. It refers to the worldwide network of voice-carrying telephone infrastructure, including privately-owned and government-owned infrastrucure.

  • Push Notification

    A push notification (also known as a server push notification) is the delivery of information to a computing device from an application server where the request for the transaction is initiated by the server rather than by an explicit request from the client. While 'push notification' is most often used to refer to notifications on mobile devices, web applications also leverage this technology.

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  • Rate Limiting

    Rate limiting happens when a recipient mail server doesn't allow emails to be delivered at the same rate as they were sent.
  • React

    React (or sometimes ReactJS) is a JavaScript library for building user interfaces. It's sometimes also referred to as a framework.


    The library focuses on creating declarative UIs using a component-based concept. Although React is often connected to front-end JavaScript development it can also be used to render views server-side in Node.js or power mobile apps using React Native. While React is open source, it is mainly developed by Facebook.

  • Reconfirmation Email Campaigns

    A reconfirmation email, otherwise known as a re-opt in email, reminds clients you correspond with about your business.
  • Reputation Monitoring

    We base your email monitoring reputation on your bounces, blocks, spam, invalid email, and successfully delivered emails.
  • Request

    A request is recorded every time an application attempts to send an email through SendGrid's servers.
  • Reseller Email Account

    Some companies may resell SendGrid's services by having a formal Reseller Partnership with SendGrid.
  • Reserved Fields

    Reserved fields are those custom fields that cannot be deleted and do not count towards your allotment of 60 custom fields. They include fields such as email, first_name, and last_name in Marketing Campaigns.

    A REST API allows software programs to expose functionality and data to other programs over the Internet in a consistent format. APIs are considered RESTful if the means of accessing the API provider's functionality adhere to the architectural style of REST.

  • Reverse DNS

    Reverse DNS is a method of resolving an IP address into a domain name.
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  • Scheduled Emails

    Scheduling emails allows the ability to have the email send process to begin at a certain time
  • SDK

    A software development kit, or SDK, is a downloadable software package that contains the tools you need to build on a platform.

  • Segmentation

    The practice of separating different types of email traffic.
  • Segments

    Segments are dynamic collections of Marketing Campaigns contacts grouped together, or segmented, based on the criteria you define.
  • Sender authentication

    Sender authentication refers to the process of showing email providers that SendGrid has your permission to send emails on your behalf.
  • Sender ID

    Sender ID is an email authentication standard developed by Microsoft that compares the email sender’s “From” address to the IP address to verify that it is authorized to send email from that domain.
  • Senders

    Senders in Marketing Campaigns provide identity information about where the emails are coming from for their recipients in campaigns in order to ensure all CAN-SPAM regulations are followed.
  • SendGrid Message ID

    The SendGrid Message ID is a unique identifier generated and assigned by SendGrid for event identification purposes.
  • Sends

    Sends relate to your requests to deliver email to your recipients through SendGrid's API or UI, which you can schedule or retrieve aggregate data from.
  • Sentiment Analysis

    Sentiment Analysis, or opinion mining, is the process of determining whether language reflects positive, negative, or neutral sentiment. Using sentiment algorithms, developers and brand managers can gain insights into customer opinions about a topic.

  • Serverless Architecture

    Serverless architecture (also known as serverless computing or function as a service, FaaS) is a software design pattern where applications are hosted by a third-party service, eliminating the need for server software and hardware management by the developer. Applications are broken up into individual functions that can be invoked and scaled individually.

  • Session Initiation Protocol (SIP)

    Session Initiation Protocol (SIP) is a signalling protocol for initiating, terminating, and modifying user sessions over an IP network.  Most commonly, SIP is used for Voice Over IP (VoIP) services, but is also often used for other communications sessions such as video calls and instant messaging sessions.

  • Short Code

    A short code is a special telephone number designed for high-throughput, two-way messaging. Short codes are used to send and receive SMS and MMS messages to and from mobile phones. Twilio currently offers short codes in multiple countries. Their name is derived from the fact that they are shorter (usually five to six digits) than their ten-digit long code counterparts.

  • SIM

    The acronym SIM stands for Subscriber Identification Module. A SIM is used to authorise a subscriber to access a mobile network. SIMs can come in many form-factors, including cards and chips.

  • Single Send

    A Single Send is a one-time email used to communicate a variety of nonautomated messages.

    A SIP INVITE is a SIP request message that initiates a SIP call. 


    A SIP INVITE is made up of lines of text. The first line in an INVITE is called a Request-Line, which is followed by more lines of text called "headers". The headers contain information about the INVITE, such as the identity of the caller, whether the INVITE was forwarded before being sent to the recipient, and the number of times a call may be forwarded. 

  • SIP Trunking

    What is SIP Calling?

    SIP (Session Initiation Protocol) trunking refers to phone calls that are routed over the Internet rather than traditional phone lines. SIP calling, therefore, refers to the act of placing calls via a SIP trunk. Because SIP calls take place across the Internet, they tend to be cheaper and more efficient than calls placed through traditional phone systems.

    Physical connections to a phone company are eliminated with the use of a SIP trunk. Using SIP trunks, a SIP provider can connect multiple channels to your private branch exchange (PBX) system, allowing you to instantly provision global voice connectivity for your Voice-over-IP (VoIP) infrastructure.

  • SMS

    SMS stands for Short Message Service and is another name for a text message. An SMS is generally sent from one mobile device to another over the cellular network. SMS is a text-only standard first formalized in 1985 in the Global System for Mobile Communications (GSM) standards.


    A SMS API is well-defined software interface which enables code to send short messages via a SMS Gateway.

    As the infrastructures for SMS communications and the internet are mostly divided, SMS APIs are often used to 'bridge the gap' between telecommunications carrier networks and the wider web.  SMS APIs are used to allow web applications to easily send and receive text messages through logic written for standard web frameworks.

  • SMS Character Limit

    The character limit for a single SMS message is technically 160 characters. However, most modern phones and networks support message concatenation: they split large messages into individual SMS messages (called "segments") and then re-create the large message at the receiving end. The 160-character limit is for messages encoded using the GSM-7 character set. Messages not encoded with GSM-7 are limited to 70 characters.

    Twilio's platform supports long messages up to 1600 characters across all Programmable Messaging channels, including SMS. However, for SMS messaging, Twilio recommends sending messages that are no more than 320 characters to ensure the best deliverability and user experience. See this article for details.

  • SMS Delivery

    SMS Delivery is a measure of the percentage of outgoing SMS and MMS messages which are received at their intended destination.  While sometimes referring to the status of a single message, SMS delivery usually is a rate of delivered versus intended messages and summarized as an 'SMS Delivery Rate.'

  • SMS Gateway

    An SMS Gateway enables a computer to send and receive SMS text messages to and from a SMS capable device over the global telecommunications network (normally to a mobile phone). The SMS Gateway translates the message sent, and makes it compatible for delivery over the network to be able to reach the recipient.

  • SMS Notifications

    SMS Notifications are out-of-band text messages sent in response to events or transactions which occur somewhere else. While often used as a marketing tool to increase the percentage of returning visitors, SMS notifications are very useful for organization and public safety purposes as well.

  • SMS Tracker

    An SMS tracker is software that uncovers detailed information about the delivery and content of text and picture messages. It allows anyone to analyze an individual message or group of messages to see delivery patterns, encoding details, and error conditions.


  • SMTP

    SMTP is an acronym for Simple Mail Transfer Protocol. SMTP is a process and set of guidelines for sending email.

    SMTP API is an API that allows you to tag your emails and provide customized email handling instructions on a per email basis.
  • SMTP Provider

    An email SMTP provider helps deliver large amounts of email from your server to the recipient’s server.
  • SMTP Relay

    An SMTP relay is used to send email between SMTP servers, when the servers are located on different domains.
  • SMTP Server

    SMTP server (Simple Mail Transfer Protocol) is an applications used to send email and react to response codes from receiving servers.
  • SMTP Service

    An SMTP service ensures delivery of your email at scale.
  • Spam

    The most simple way to define spam in the Email world is by using these 2 words unwanted email.
  • Spam Filter

    Software based email filters that look for spam and block it from going to the inbox.
  • Spam Reports

    Spam Reports are triggered when a customer marks a message as spam in their email client.

  • Spam Traps

    A SPF is an email authentication standard that helps ISPs better identify legitimate email senders.
  • SPF

    SPF is an email authentication standard that helps ISPs better identify legitimate email senders.
  • Spoofing

    Spoofing is a technique where forged email addresses are used to trick recipients into opening an email because the source has been hidden
  • Sticky Sender

    Sticky Sender is a valuable feature for SMS or Voice marketing where all outbound customer contact comes from a single number. This 'sticky' or 'unchanging' number increases customer familiarity and trust. With a two-way Voice or SMS system, it also allows customers to contact businesses and organizations through the very same number.

  • String Identifier (SID)

    A String Identifier (SID) is a unique key that is used to identify specific resources.

  • Subscriber List Management

    Managing your subscriber list is key to keeping your subscribers happy.
  • Suspicious Sender

    A suspicious sender is a sender who sends email to recipients who have not given them express permission to do so.
  • System Fields

    System fields are available in the campaign builder that allow you to insert specific content into your campaign, such as web links, unsubscribe links, or links to your campaign's subscription preferences page. These system substitution tags are not related to your contact data and should not be confused with reserved or custom fields.
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  • TCPA

    The TCPA (Telephone Consumer Protection Act) is a federal statute enacted in 1991 designed to safeguard consumer privacy. This legislation restricts telemarketing communications via voice calls, SMS texts, and fax.

  • Teammates

    Manage multiple users on one SendGrid account.
  • Throttling

    Learn more about deferrals and throttling
  • Timezones

    Local time, based on your current geographic location on the earth.
  • TOTP

    TOTP stands for Time-based One-Time Passwords and is a common form of two factor authentication (2FA). Unique numeric passwords are generated with a standardized algorithm that uses the current time as an input. The time-based passwords are available offline and provide user friendly, increased account security when used as a second factor.

  • Transactional Email

    Transactional Emails represent the emails which are triggered by a user interacting with a web application.

  • Transactional Email Templates

    Transactional email templates are pre-coded email layouts that anyone can use to easily create and send transactional emails.
  • Transport Layer Security

    Protect transmission of email information with TLS and SendGrid
  • Transport Layer Security (TLS)

    TLS, or Transport Layer Security, is a widely used cryptographic protocol that ensures data security during communication over a network. The TLS protocol, like its predecessor SSL (Secure Sockets Layer), is primarily designed to enable reliable, authenticated, and secure communication between two or more computer applications. In modern browsers, connections secured with TLS are usually indicated by a lock icon next to the URL.

  • Triggered Actions

    Triggered Actions are initiated by a triggering event.
  • Triggered Email

    Triggered emails are another name for automated emails that are triggered by specific events or actions.
  • Trusted Sender

    A trusted sender is a sender who only sends email to those recipients who have given them express permission to do so.
  • Twilio Markup Language (TwiML)

    TwiML, or the Twilio Markup Language, is an XML based language which instructs Twilio on how to handle various events such as incoming and outgoing calls, SMS messages and MMS messages.  When building a Twilio application you will use TwiML when communicating your desired actions to Twilio.

  • Two Factor Authentication

    Multi-factor Authentication requires the user to have some information that only they could have to log into an account.
  • Two Factor Authentication (2FA)

    Two-factor authentication (commonly abbreviated 2FA) adds an extra layer of security to your user’s account login by requiring two types of authentication. This is usually something your user knows and something they have.

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  • UCS-2

    UCS-2 is a character encoding standard in which characters are represented by a fixed-length 16 bits (2 bytes).  It is used as a fallback on many GSM networks when a message cannot be encoded using GSM-7 or when a language requires more than 128 characters to be rendered.

  • Undelivered Email

    Email can be undelivered for various reasons, including an issue with email address or content.
  • Unicode

    Unicode is an international character encoding standard that provides a unique number for every character across languages and scripts, making almost all characters accessible across platforms, programs, and devices.

  • Unknown User

    Bounced - Unknown User is an error indicating the email address does not exist.
  • UTF-8

    UTF-8 is a variable-width character encoding standard that uses between one and four eight-bit bytes to represent all valid Unicode code points.

  • UTM Parameters

    Defintion of UTM Parameters
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  • Virtual Phone Number

    A virtual phone number is a standard telephone number that is not locked down to a specific phone. A virtual number can route a voice call or text message to any phone or workflow. With virtual numbers powered by an API, complex software workflows can be built that are triggered by calls and texts.

  • Virtual SMS

    Virtual SMS enables you to send and receive SMS text messages over the internet without having to use a physical phone. This is especially useful when you want to use software to communicate with telephone networks that would be impossible on a physical phone, e.g. Uber notifying a customer that their car is outside or to have local phone numbers in different countries.

  • Voice API

    A voice API is a tool for software developers to make and receive phone calls with a simple, easy to understand API. Behind the scenes, a voice API bridges the Public Switched Telephone Network (PSTN) and applications connected to the internet. By using a voice API, software developers can program voice calling into their applications without specialized telecommunications knowledge and hardware.

  • Voice Proxy

    Voice Proxy is the technique used to protect users’ private information by providing an intermediary number so that neither sender nor receiver can see the other’s true phone number during voice calls or SMS exchanges.

  • Voice Trace

    Voice trace is a voice quality troubleshooting feature that captures the media stream for calls and stores them for Twilio Support to use in their investigations. 

  • VoIP (Voice Over IP)

    Voice Over Internet Protocol (VoIP) is a category of hardware and software that enables voice calls to be made and received over the internet.

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  • Web API

    Web API allows web servers and web browsers to easily interface with each other to enable account and data collection for services such as email.
  • Webhook

    Webhooks are user-defined HTTP callbacks. They are triggered by some event in a web application and can facilitate integrating different applications or third-party APIs, like Twilio.

  • WebRTC

    Web Real-Time Communication (WebRTC) is a collection of communications protocols and APIs originally developed by Google that enable real-time voice and video communication over peer-to-peer connections.

  • WebSockets

    A WebSocket is a persistent bi-directional communication channel between a client (e.g. a browser) and a backend service. In contrast with HTTP request/response connections, websockets can transport any number of protocols and provide server-to-client message delivery without polling.

  • Whitelabel

    Refers to the process of showing ISPs that SendGrid has your permission to send emails on your behalf.
  • Workforce Optimization

    Workforce Optimization (WFO) is the process of performing quality checks to ensure that all a company staff’s interactions with its customers are performed to the same standard

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  • X-Message-ID

    The X-Message-ID is a header returned when sending email from SendGrid.

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  • 7-bit Encoding

    7-bit encoding is the same as Ascii encoding: both represent alphanumeric characters and symbols as numbers.

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