554 5.6.0 Gmail bounce: malformed message
What 554 5.6.0 means
The message does not follow RFC 5322, so Gmail refuses to accept it.
Message text
Email message is malformed. Not accepted…
This is an excerpt: the provider's documentation shortens the message. Full text: provider documentation
Common causes of 554 5.6.0
- Message format breaks RFC 5322 rules
- Malformed headers or body in the message
How to fix 554 5.6.0
- Check the message source with email header analyzer for malformed headers.
- Fix the sending software so it produces RFC 5322 compliant messages.
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How to read 554 5.6.0
The first part, 554, is the SMTP reply code. Transaction failed: a general permanent failure, often a policy or reputation block. Replies that start with 4 are temporary and replies that start with 5 are permanent (RFC 5321 §4.2.1).
The second part, 5.6.0, is an enhanced status code (RFC 3463 §2) written class.subject.detail. Class 5 is a Permanent failure (5xx): the command was rejected and the sender should not repeat it unchanged (RFC 5321 §4.2.1; RFC 3463 §2).. Subject 6 is message content or media: the message content could not be accepted. The detail number refines the subject, and providers may define details of their own, which is why one code can read differently at Gmail, Microsoft and Yahoo.
Do not keep resending the same message: a permanent failure repeats until the cause is fixed. Correct the cause, then send a new message.
Official source: knowledge.workspace.google.com. Last verified 2026-10-20.
Related guides
- How to create an SPF record (syntax and examples)
- How DKIM works and how to publish a DKIM record
- How to set up a DMARC record, from p=none to p=reject
Related codes
- 5.6.11 Microsoft: invalid characters
- 550 5.7.26 Gmail: blocked by dmarc policy
- 550 5.7.26 Gmail: no spf or dkim pass
- 550 5.7.26 Gmail: SPF hard fail
- 550 5.7.27 Gmail: SPF not passed
- 550 5.7.25 Gmail: no PTR record
FAQ
What does 554 5.6.0 mean?
The message does not follow RFC 5322, so Gmail refuses to accept it. This is a permanent failure.
How do I fix 554 5.6.0?
Check the message source with email header analyzer for malformed headers. Fix the sending software so it produces RFC 5322 compliant messages.
Is 554 5.6.0 permanent, and should I retry?
554 5.6.0 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.