Question : mail problem between Sendmail and Exchange server

Information:
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I have two subnets.
The Exchange server is at one subnet and a Linux box that will be used to host Bugzilla is at the other subnet. We use WINS instead of DNS. Only Exchange server has DNS entry in ISP. Linux box uses /etc/hosts, configured with sendmail, without a DNS entry in ISP. Both machine can ping each other with names.

When users access Bugzilla through the web, some information may need to send email to the someone who has the account in the Exchange server.

Problem:
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The users in Linux box can send email out to the Internet like hotmail or yahoomail, but they fail to send email to the Exchange server. The Exchange server can not send mail to the Linux box either. What's the problem? Will adding a MX entry for the Linux box in the ISP fix the problem?

Answer : mail problem between Sendmail and Exchange server

I can think of several reasons as to why Linux may not be delivering email to the Exchange server. One possibility is that Exchange may be rejecting the messages because it can't do a reverse lookup on the Linux box's IP, which you'd fix by getting your ISP to add A & PTR records for the Linux box. Another possibility is that the Linux box may be confused as to what to do with the mail. How are the messages being addressed (e.g., [email protected] or [email protected]) and what is the FQDN (Fully Qualified Domain Name) you've assigned to the Linux box?

You should check to see if email to Exchange is simply being queued on the Linux system ("mailq" will tell). Also /var/log/maillog should have any errors relating to email transfers as reported by sendmail. If you can show me the error that sendmail logs I'm sure we can determine what the problem is.