Too many hops errors on smtp

[MTSU_SAN]

This afternoon we started getting "too many hops" errors from sendmail, even when sending mail between clients on campus. I thought it was because I might have changed sendmail.cw, but that file was fine, permissions and content-wise. What other things could cause this error?

[Richard Steven]

Without seeing the error I can only offer possibilities:

Check the Received headers.

You're routing the mail to a host that doesn't know what to do with it other than sending it back.

You should be able to find the misconfiguration by checking the involved hosts.

Has your DNS changed?

[MTSU_SAN]

The DNS would have been my first thought, too, but my Networking guys say nothing changed--all of the headers are bounces from my mail server to itself--it doesn't recognize itself. Like this:
Received: from frank.mtsu.edu (frank.mtsu.edu [161.45.193.16])
by frank.mtsu.edu (8.11.1/8.9.3) with ESMTP id gA1Ipbf28789
for ; Fri, 1 Nov 2002 12:51:38 -0600 (CST)
Received: from frank.mtsu.edu (localhost [127.0.0.1])
by frank.mtsu.edu (8.11.1/8.9.3) with ESMTP id gA1IpOS28198
for ; Fri, 1 Nov 2002 12:51:26 -0600 (CST)
Received: from frank.mtsu.edu (frank.mtsu.edu [161.45.193.16])
by frank.mtsu.edu (8.11.1/8.9.3) with ESMTP id gA1Iolf26399
for ; Fri, 1 Nov 2002 12:50:48 -0600 (CST)
I restarted Sendmail, and it stopped, but I don't want it to happen again!

[Ron Kinner]

Perhaps the following from:

http://www.ezine.com/QandA/Hops.html

will help:

"One of the most common problems encountered when setting up DNS and SMTP e-mail is that the SMTP server refuses to accept the e-mail messages. A specific symptom is that someone from outside your network sends you e-mail and the mail comes back with an error message referring to "too many hops".

When you place an MX record for your domain into your DNS zone file you are telling e-mail systems out on the net to send mail for your domain to a specific SMTP server for delivery. This is only half of the setup - you also need to tell the SMTP server to accept the e-mail.

The "too many hops" error occurs when the mail is delivered to the SMTP server but the server does not know that it should keep mail for that address. It looks up the MX record and tries to relay the mail on to the destination. Each time mail is forwarded by an SMTP server, the server increments a counter. After this happens enough times the SMTP server Maximum Hop Count parameter is exceeded and the mail is returned to the sender as undeliverable.

When most SMTP servers are loaded they automatically configure themselves to accept mail that is addressed to the computer on which they are running. If the computer is named Mail.Company.Com then the SMTP server will accept mail addressed to recipients @Mail.Company.Com. To get the SMTP server to also accept mail addressed to recipients @Company.Com usually requires additional configuration. For example on Microsoft Exchange you need to add the Domain Name (Company.Com) as Inbound. You will need to consult the documentation for your specific SMTP server for the details on how to do this on your SMTP server. "

Ron