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Re: Yahoo Mail problems ? (queue issues in general)

  • From: Valdis.Kletnieks
  • Date: Wed May 05 13:29:25 2004

On Wed, 05 May 2004 10:59:55 EDT, Mike Tancsa <mike@sentex.net>  said:

> Anyone else seeing Yahoo mail queue up today ?    Some of their servers 
> respond in about 10secs with the HELO banner, most others take more than 
> 2m.   Because of the recent increase in SPAM, I was looking to reduce the 
> wait time for the initial HELO to 2m from 5m. However, the RFC calls for 5m 
> on the HELO and another 5m for the MAIL command.

Do you have a handle on whether the delay is between the first SYN packet and
finally completing the 3-packet handshake, or is it between that and when the
220 banner actually arrives?  Or are both phases an issue?
 
> Having a process block like that for up to 10m seems a bit excessive to 
> deliver one email (and its probably a bounce to boot!).  What are others 
> doing?  This problem seems to becoming more and more acute.

What I do is the *first* attemt to deliver the mail has a highly-non-compliant
5 second timeout (which is just enough for an initial SYN, 2 retransmits, and a
few hundred ms budget for RTT for a SYN+ACK) for the 3-packet handshake, and
then subsequent retries in the background are given a longer 5-min timeout. (I
gathered some stats for quite sime time before deploying that - out of several
million connection attempts, I found less than a dozen that took over 5 seconds
that did in fact complete in under 5 minutes). Once the 3-packet handshake
succeeds, they then get a 5 minute timeout to get the 220 banner out.  Probably
not perfect, but it's close enough to keep the queues manageable...

Also, YMMV, so gather your own stats....

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