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sendmail pauses for connections... what is it doing?
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gilesc
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Joined: 01 Dec 2002
Posts: 40

PostPosted: Sat Apr 05, 2003 12:56 pm    Post subject: sendmail pauses for connections... what is it doing? Reply with quote

I get weird sendmail connection delays when connecting from other domains, for instance if I start a connection to the SMTP service I get this:

Code:
root@remotehost:~# telnet mail.example.com 25
Trying 1.2.3.4...
Connected to mail.example.com.
Escape character is '^]'.
There is then quite a delay before I get the reply:
Code:
220 gate.example.com ESMTP Sendmail 8.12.9/8.12.8; Sat, 5 Apr 2003 13:50:15 +0100
^]
telnet> quit
Connection closed.
root@remotehost:~#


Does anyone have any idea why this happens. I'm guessing it is because the machine thinks of itself as gate.example.com and not mail.example.com.
Is there any way to get rid of this delay? and by doing so do I affect the security of my relay in any way?
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caffiend
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Joined: 26 Mar 2003
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Location: Oakland, CA

PostPosted: Sat Apr 05, 2003 3:26 pm    Post subject: Reply with quote

sounds to me like sendmail is trying to do a reverse lookup when a foreign host connects and is timing out.

Make sure you have DNS configured correctly on you server.
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gilesc
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PostPosted: Sat Apr 12, 2003 12:37 pm    Post subject: Reply with quote

Actually doing a reverse lookup on the source IP is much quicker than the delay that Sendmail exhibits.

I can confirm that sendmail is doing a reverse lookup, as I have seen that traffic in a packet dump.

But why the even longer delay?
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