An email blocklist, also called a blacklist, provides data receiving mail servers can use when filtering messages. DNS blocklists can list IP addresses or domains, for example. The receiving server decides whether and how to act on a match.
What does a listing mean?
It depends on the purpose of the list. One list might track observed spam activity. The Spamhaus Policy Blocklist can also include IP ranges that, by policy, should not send directly to other mail servers. Such a listing is not evidence of spam. Depending on the receiving server’s configuration, a match can lead to rejection, spam classification, or further checks.
How do you investigate a rejection?
If a bounce message names a blocklist, note the domain or sending IP and the exact list name. A lookup tool can help narrow down the issue. Then check the reason with the list operator, and contact your sending service if you use a shared IP. A removal request alone does not resolve the underlying cause.
How is a newsletter suppression list different?
A newsletter suppression list acts on the sender’s side: it prevents sending to certain recipients. A DNS blocklist gives the receiving service a signal about the incoming message or its source.
