Hello,

has anybode an idea why the MS SMTP service delivers some emails from time
to time up to 40 times? Exactly the same email that is only beeing sent once
is delivered between 20 and 40 times within a few minutes.

I have to say that my SMTP works under very high load. It receives several
100,000 emails within an hour created with a newsletter sending tool on
another server. The newsletter tool connects with my STMP on 30 parallel
channels to maximize the delivery rate. The server is part of a 3-server
group that deliver load balanced. But on the other servers I can't see such
a behavior. Only on one of them, and I previously sent that amount of emails
many times, but the latest mailing was with that troubles. I didn't change
any settings in the meantime.

Can anyone help?


Regards,

Chris

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>The server is part of a 3-server group that deliver load balanced. But on the other servers
 I can't see such
>a behavior.

If you have three identical servers being hit with the same incoming
load, but one of them is doing SMTP-level retransmissions, the most
probable cause is that there also network- or NIC-level issues causing
incomplete, half-closed sessions.

--Sandy

[ Post a follow-up to this message ]

Sandy,

> If you have three identical servers being hit with the same incoming
> load, but one of them is doing SMTP-level retransmissions, the most
> probable cause is that there also network- or NIC-level issues causing
> incomplete, half-closed sessions.

How can I find out where the problem exactly is located at? I didn't find
anything suspect in the eventlogs, only the hundreds of delivery failure
messages (of email addresses that do no longer exist).

The only thing I was able to trace is, that the SMTP doesn't accept any more
emails when this problem occurs. That stops my newsletter tool sending
emails to that SMTP, but a few minutes later I can use it like before. Most
of the emails are delivered correctly, only a few dozens recipients of about
100,000 in total get their newsletter up to 40 times.


Regards,

Chris

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