Error writing SMTP packet error

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What does "Error writing SMTP packet" mean and how do I troubleshoot this?

"Error writing SMTP packet" means the TCP stack returned an error response to a network write. The most common cause of this problem is that the SMTP server at the other end dropped the connection.

Another common cause is that the network connection between the local messaging server and the remote SMTP server has encountered a problem e.g. firewall or proxy software/network connectivity issue/very slow throughput.

Although much more rare, the problem can also lie in the client TCP stack.

Diagnosing the root cause can be very difficult given the nature of the likely causes. Ideally the problem needs to be addressed at the remote end to see if there are problems with the remote SMTP server (due to say excessive load, problems with virus scanners, border gateway issues, email appliance problems etc.)

Isolating where the problem exists e.g. for just large emails, at certain times of the day, for the same email domain may also help isolate a possible cause.

From the client side, you can enable master_debug on the outgoing channel (e.g. tcp_local) to see if that provides some insight as to where in the SMTP dialogue things are failing. Enabling network packet tracing may also provide insight as to when the problem occurs and if it is due to a timeout at the other end (e.g. the connection is dropped after exactly 10 minutes each time).

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Applies to: Messaging Server 5.2 and above
Answered by: Shane H., Dan N., Ned F.
Date initially answered: June 29, 2007