What is Blocklist?
A blocklist is a database of IP addresses or domains reported for sending unwanted or abusive email, which receiving servers consult to decide whether to reject or filter a message.
Lists are run by different organisations with different rules. Some are minor and have little effect, while a listing on a major one can cause widespread rejections. Bounce messages usually name the list that triggered the refusal.
Common causes include hitting spam traps, high complaint rates, sending to old or purchased addresses, and a compromised account. Shared IPs can also be affected by other senders on the same address.
The remedy is to find the cause first. Pause the problem sending, clean the list, and fix the underlying issue, then follow the list's own delisting process. Asking for removal without fixing the cause usually leads to being listed again.
A worked example.
A hypothetical homeware shop sees a burst of rejection bounces citing a blocklist. Investigation shows that an old competition list was imported and included recycled addresses. The team suppresses that import, sends only to recent buyers, and then requests delisting.
Common mistakes.
- Requesting removal before fixing the cause
- Ignoring the bounce text that names the list
- Importing old lists without checking their age and source
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