Blocklist: what it means

An email blocklist (once commonly called a blacklist) is a database of IP addresses or domains that have been linked to spam or abuse. Mail servers and spam filters query these lists, usually through DNS, when deciding whether to accept, filter or reject a message. Some lists are widely trusted and can cause real delivery failures; others are small or little used and have almost no effect.

Listings usually follow a pattern rather than a single mistake. Hitting spam traps (often from bought, scraped or very old lists), sudden bursts of complaints, or a compromised account sending junk are the most common causes. Domain blocklists can also list a domain that appears in the links of an email, which is one reason why using a shared or unknown link shortener can hurt you.

If you send through a shared IP on an email platform, the IP is managed by the platform, and their team handles IP-level listings. Your domain, however, is yours. Watch for a sudden rise in bounces with messages that mention a list by name, or a drop in delivery to one provider. Check your sending domain and, if you have one, your dedicated IP against the major lists.

Getting delisted starts with fixing the cause. Removal requests are usually made on the list operator’s website, and reputable lists expect you to explain what went wrong and what you changed. Requesting removal while the problem continues often leads to a longer listing. Stop sending to the suspect segment, remove unengaged and unverified addresses, and only then ask to be removed.