550 5.7.29 Gmail bounce: tls connection required
What 550 5.7.29 means
Gmail refused the message because it was not sent over an encrypted TLS connection.
Message text
This message was blocked because it wasn't sent over a TLS connection.
Common causes of 550 5.7.29
- Sending server does not use STARTTLS for outgoing mail
How to fix 550 5.7.29
- Turn on STARTTLS for outgoing SMTP in your sending software or server.
- Send again once TLS is working.
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How to read 550 5.7.29
The first part, 550, is the SMTP reply code. Requested action not taken, mailbox unavailable: the mailbox does not exist, is not allowed, or the message was refused for policy reasons. Replies that start with 4 are temporary and replies that start with 5 are permanent (RFC 5321 §4.2.1).
The second part, 5.7.29, 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 7 is security or policy: authentication, authorization or policy refused the message. 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
- 5.7.0 SMTP: security status
- 5.7.1 SMTP: delivery not authorized
- 5.7.23 SMTP: SPF validation failed
- 5.7.25 SMTP: reverse DNS failed
- 5.7.26 SMTP: authentication failed
- 5.7.27 SMTP: sender has null MX
FAQ
What does 550 5.7.29 mean?
Gmail refused the message because it was not sent over an encrypted TLS connection. This is a permanent failure.
How do I fix 550 5.7.29?
Turn on STARTTLS for outgoing SMTP in your sending software or server. Send again once TLS is working.
Is 550 5.7.29 permanent, and should I retry?
550 5.7.29 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.