Blocklists
To help determine if an email message comes from a trusted sender, many inbox providers, like Yahoo and Hotmail, and private organizations use blocklists.
By checking sender information against known bad actors on blocklists, the receiving server can choose what action they want to take. They can reject, filter, or throttle email from that sender.
To determine if a blocklist includes your IP address or domain, monitor your email activity or webhook data for block events that indicate a listing. Hundreds of blocklist providers exist, but [few impact most email senders][bl-providers].
Blocklist providers monitor for various signals and behavior. To determine a sender's sending behaviors, these providers might operate [spam traps][spam-traps]. Blocklists monitor networks of these spam traps for poor sending behaviors. These behaviors might indicate spamming, fraud, phishing, or list bombing.
If sending behaviors exceed certain thresholds, blocklist providers add the sender's IP address, from address, or both to their list. Providers don't provide detailed information regarding the listing causes like spam trap address that triggered the delisting. Providers often provide subject lines, from addresses, and the dates when the providers received messages. They do provide guidance as to which actions to take before they can delist your addresses.
Remedy blocking issue before requesting delisting
Never request delistings repeatedly without making changes to your email project. If you don't the behavior that caused the delisting, the provider might ignore your delisting requests.
If you notice a block message from Spamhaus based on one of our IP addresses, know that Twilio and Spamhaus are addressing the issue. Don't make another request through Twilio support.
As these plans use shared IP addresses, Twilio can't move your account to another IP pool because one or more IP addresses in a shared IP pool made it on a blocklist.
Twilio monitors the health of its shared IP pools. This includes monitoring for shared IP addresses added to reputable blocklists. When Twilio detects a shared IP address added to a blocklist, it analyzes that IP address. It then checks if the listing is causing measurable deliverability issues. If Twilio detect issues, it mitigates the listing.
A number of IP addresses blocklists frequently get listed then delisted shared IP addresses. Even senders with impeccable sending practices find themselves on a blocklist at some point. Whether you use shared IP addresses or dedicated IP addresses, blocklists are part of the business of email. Not all listings can be remediated, especially those with minimal impact.
If you discover your Twilio SendGrid IP address on a blocklist, make the delisting request first. Twilio assigns these IP addresses to one account only. Twilio expects you to take responsibility for all of the mail sent through your account. If the listing services requires it or you find the form too difficult, Twilio can assist with these delisting requests.
Info
If someone added your domain, and not your IP address, to a blocklist, the domain administrator must make the delisting request.
To check on the status of your IP address, you can use one of these aggregation websites:
To remove your IP address or domain from a blocklist, see the following provider resources:
Fix the behavior that got you on the blocklist. If you ask for delisting without fixes, you might find your IP address back on the blocklist. Each delisting becomes more difficult after the second or third listing.
To learn more about how to avoid being added to a blocklist, see What Are Email Blocklists (and How to Avoid Them).