Blocklist rejection
Also called: DNSBL, blacklist rejection, RBL
A rejection issued because the sending IP or domain appears on a list the receiving server consults. These normally arrive as a permanent SMTP failure — most often 554 — with the reason in the response text.
In plain terms
You were refused because of who is sending, not who you are sending to.
Why it matters for deliverability
Blocklist rejections are about your infrastructure rather than your recipients, so the usual list-hygiene reflex does not help. Suppressing the addresses would remove perfectly good subscribers while leaving the actual problem in place.
What to do about it
- Read the full rejection text — it almost always names the list or links to a policy page.
- Check the named list's own lookup tool for your sending IP before doing anything else.
- Fix the cause, then request delisting. Delisting without fixing it relists you.
- Do not suppress the recipients; they were never the problem.
Source
RFC 5321 — Simple Mail Transfer Protocol (the 554 permanent-failure reply used for these rejections)
“554 Transaction failed (Or, in the case of a connection-opening response, "No SMTP service here")”
Checked 2026-08-29
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