Why does smtp see extra input after a message is received?

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Question

When sending mail to an external server from my GMS server, I always see failures in the log. Messages appear to be sent OK, but SMTP on the receiving server seems to see an extra blank line followed by a dot on a line by itself. There is no sign of this being sent by the post service on my server.

I do not see this when sending mail to localhost.

Answer

GMS software carries out a considerable amount of checking and correction to incoming messages in order to make them Standards Compliant as far as possible.

In a particular case, one piece of the compliance code added an extra terminator to an email message as it was posted out. This resulted in the message being sent correctly to the remote server, followed by an extra message terminater. The remote system responded with a success and an immediate error message, showing that the message was sent successfully. Due to the error message, th GMS delivery service stopped attempting to send the next message on that connection, then made another connection to send the next queued message for that domain.

The net result of this was an increase in the time taken to send messages to domains which received a lot of email from your server.

There are two solutions:

  • Recommended Upgrade to the latest version of software.
  • Set the default "retry time" for posting email to 1 minute. This increases the load on your system slightly, but ensures that email is delivered correctly.

NOTE: This issue does not cause any email to be lost.

See Also:

Keywords:SMTP, POST, CRLF, dot, terminating,CR,LF

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