MTU??

[wel...@gmail.com]

timeout waiting for input from <HOST> during message collect

Any indication of what this error really means? If you think it is
distant end MTU related any idea of how to prove that without access to
there kit.

John

[Robert Harker]

> timeout waiting for input from <HOST> during message collect

This means that as the sendmail server was receiving (collecting)
the message the data transfer stopped. This could happen for many
reasons, the remote host going down, a network error, stateful
firewall issues, etc...

Are you seeing it a lot? Are you seeing it from a specific host
or domain? Do you have any feeling for the size of the message?
small, large, or powerpoint size?

It should not harm anything since the SMTP client should just resend
it.

Hope this helps

RLH

> For info about our "Managing Internet Mail, Setting Up and Trouble <
> Shooting sendmail and DNS" and a schedule of dates and locations, <
> please send email to in...@harker.com, or visit www.harker.com <

Robert Harker Harker Systems
Sendmail and TCP/IP Network Training 4182 Plesant Hill Rd.
Sendmail, Network, and Sysadmin Consulting Lincoln, CA 95648
har...@harker.com 530-887-9990

[Yizhar Hurwitz]

HI.

Yes, this issue could be MTU related.
It can be caused by either side - your side or the other.

It is a bit dificult to prove because such symptoms are not always easy to reproduce.
One way to further investigate and solve it is trial and error.

I suggest that you configure your server with MTU of 1300 instead of the default 1500.
I think that 1300 is the best default for mail server (and other internet facing servers), unless a lower value is
needed.
If this solves the issue then go ahead and keep it that way - my recommendation is to use 1300 (or lower) as a default
even if everything seems to work fine.

You can test MTU limits with commands such as:

ping -f -l 1500 ....

However there are many firewalls that block or filter ICMP packets so you should consider this as additional
troubleshooting tool but not as a "proof" for something.

You can also send email to "the other side", suggesting to their mail server administrator to check and modify their
MTU.

Have you read this:?
http://www.sendmail.org/tips/pathmtu.html

--
Yizhar Hurwitz
http://yizhar.mvps.org

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