Glossary
SMTP 554
A generic permanent failure for the whole transaction. When it appears as the response to opening a connection, it means the host offers no SMTP service at all.
In plain terms
A flat refusal, with no more specific reason given.
Why it matters for deliverability
554 is where most blocklist and reputation rejections land, because it is the catch-all permanent failure. The number tells you almost nothing; the text after it usually tells you everything.
What to do about it
- Always log the full response text, not just the code.
- Look for a blocklist name or a policy URL in the text and act on that.
- Treat it as permanent for that message, but investigate before suppressing the address — the rejection may be about your IP, not the recipient.
Source
RFC 5321 — Simple Mail Transfer Protocol
“554 Transaction failed (Or, in the case of a connection-opening response, "No SMTP service here")”
Checked 2026-08-29
Related terms
Go deeper
Definitions reviewed 2026-08-29. Spotted something wrong? Tell us.
See how your own mail is handled
Run a real message through MailTester and read the authentication results, spam score and delivery signals described on this page against your own domain.