What to do
- If repeated, check MTU on the path, the firewall, and TLS compatibility.
How it appears in a bounce
450 4.4.2 Bad connectionPaste the full bounce into the decoder — it finds every code and recipient and says what to check.
SMTP 4.4.2 Bad connection
The connection broke during the session. Retried automatically.
4.4.2
- Class
- 4xx · Temporary failure
- Retried?
- Yes, the sending server retries
- Defined in
- RFC 3463