SMTP connection interrupted
The connection closed before SMTP communication completed.
What to do now
- Check for a temporary network problem.
- If it repeats, inspect the last command, server logs and connection state.
- If it closed after DATA, inspect the queue and possible duplicate delivery before resending.
Representative reply
Lost connection with mx.example.com
Retry decision
Check the interrupted stage and queue. After DATA, investigate possible duplicate delivery.
Why it happens
The network or server may close an active session.
Typical stage
CONNECT
- CONNECT
- EHLO
- MAIL FROM
- RCPT TO
- DATA
- DELIVERY
Stages vary by server. Confirm the actual stage from the complete reply and session logs.
What is SMTP Reply Code?Open only the explanations you need
Three-digit server reply: 4xx is transient, 5xx permanent. Read the complete text to investigate the cause.
What is Enhanced Status Code?Open only the explanations you need
An extended status such as 5.1.1. Server wording and usage may vary.
Check directly
- Check for a temporary network problem.
- If it repeats, inspect the last command, server logs and connection state.
- If it closed after DATA, inspect the queue and possible duplicate delivery before resending.
If you operate or diagnose the mail server, the tools below can help with these checks.
Cautions
Observed DSNs do not map one-to-one to causes. The stage shown is typical; confirm it with the full reply and actual logs.
Similar reply wording and observed status codes
lost connection with
Observed DSNs: 4.4.2