What causes "SMTP data timeout (message abandoned)"?

cPanelMichael

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Apr 11, 2011
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Hello :)

This is explained in the Exim documentation:

It means that there was a timeout while Exim was reading the contents of a message on an incoming SMTP connection. That is, it had successfully accepted a MAIL command, one or more RCPT commands, and a DATA command, and was in the process of reading the data itself. The length of timeout is controlled by the smtp_receive_timeout option.

If you get this error regularly, the cause may be incorrect handling of large packets by a router or firewall. The maximum size of a packet is restricted on some links; routers should split packets that are larger. There is a feature called “path MTU discovery” that enables a sender to discover the maximum packet size over an entire path (multiple Internet links). This can be broken by misconfigured firewalls and routers. There is a good explanation at http://www.netheaven.com/pmtu.html. Reducing the MTU on your local network can sometimes work round this problem. See Q0017 (3) for further discussion.

Thank you.
 

alexvyi

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For anyone landing on this page, MTU is important but so is MSS CLAMP. So if you are on a pppoe connection, the eth should have a MTU of 1500, pppoe 1492 and the MSS clamp should be 1412.