[nylug-talk] Strange sendmail problem.

[Michael Bacarella]

On Fri, Jul 14, 2006 at 12:02:27PM -0400, Matt Stockdale wrote:
> I'm seeing some strange (to me, anyhow) behavior from some sendmail
> installs, and I'm wondering if anyone has seen anything similar..
> 
> Basically I've got a box that is the smart host for a bunch of other
> servers. We'll call that server A. Server B is a load-balanced IP
> pointing at 3 identically configured sendmail servers, B1, B2, and B3.
> 
> What's happening is that some mail (for the sake of argument, say 20
> messages) will queue up on server A for domain foo.com. The MX of
> foo.com is server B. Server A will connect to server B, go through the
> ehlo, etc, etc, and deliver the message. When it sends .\r\n to end the
> message, instead of responding with any sort of status code (successful
> or otherwise), the real server (be it B1, B2, or B3) occasionaly just
> closes the TCP session, but with FIN and not RSET. (I've verified this
> with tcpdump).

It sounds like sendmail on server A is calling shutdown(2) on its side
of the connection to say it's finished speaking, the load balancer
is assuming this means the dialog is finished, and closes the connection
entirely.