---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/sendgrid/glossary/blocklist#article
headline: Blocklist
description: "*Email Deliverability*. A list of IP addresses, email addresses, or domains known to ISPs or list providers for sending unsolicited or unwanted emails."
url: https://www.twilio.com/docs/sendgrid/glossary/blocklist
inLanguage: en
dateModified: 2025-11-07T21:55:06.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# Blocklist

*Email Deliverability*. A list of IP addresses, email addresses, or domains known to ISPs or list providers for sending unsolicited or unwanted emails.

Private companies own and operate databases that track mailing infrastructure (domains and IP addresses) that recipients or providers identified as a source of problematic email. This includes [spam][], [phishing][], [spoofing][], and script attacks.

To identify and filter illegitimate mail streams, major ISPs, [inbox service providers][inbox] and enterprises use their own or [third-party blocklists][3bl].

Blocklisting services might impact [deliverability][]. If you [find your IP address on a blocklist][find-on-bl], then submit a [delisting request][delist].

[3bl]: /docs/sendgrid/concepts/reputation/blocklist-provider-insights

[delist]: /docs/sendgrid/concepts/reputation/blocklists#delisting-request-forms

[deliverability]: /docs/sendgrid/glossary/deliverability

[find-on-bl]: /docs/sendgrid/concepts/reputation/blocklists#check-your-ip-address

[inbox]: /docs/sendgrid/concepts/inbox-provider-insights

[phishing]: /docs/sendgrid/glossary/phishing

[spam]: /docs/sendgrid/glossary/spam

[spoofing]: /docs/sendgrid/glossary/spoofing