Running a RHEL ES5 mail server using fetchmail/sendmail.
The flow of email into our system:
01. Email goes to third party mail server. Product being used is SmarterMail Enterprise 13.0. I define our mail accounts here and set some spam rules (like block all emails ending in .ru). This is not our server. It is outside our network.
02. Our RHEL ES5 mail server fetches the email every 300 seconds. Config file = /etc/fetchmail.conf and log file = /var/log/fetchmail.log
We internal mail accounts defined on the RHEL machine. This allows the employees in the company to email each other without the email actually leaving our network. We have an internal domain as well as our corporate, external domain. All has worked for years.
03. The end user has Thunderbird installed on their workstation that fetches the mail whenever they click the button or every 5 minutes.
In the /var/log/fetchmail.log file, I see entries like:
Code: Select all
fetchmail: reading message jsmith@[our external domain]@mail.[our external domain]:1 of 2 (1444 octers) (log message incomplete)fetchmail: SMTP error: 451 4.1.8 Domain of sender address jill.smith@ryelxperepwin.rye.avon.com does not resolve
fetchmail: not flushed
An entry from /var/log/maillog:
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Jan 20 13:08:09 sendmail[18534]: t0KI44u3018534: ruleset=check_mail, arg1=<service-25093@payflowpro.com>, relay=localhost.localdomain [127.0.0.1], reject=451 4.1.8 Domain of sender address service-25093 does not resolve
01. Is this a fetchmail or sendmail issue? I am confused as to if we are receiving spam or some machine inside our network is attempting to send out spam and the domain just does not resolve.
02. One person on Google said to turn off the DNS lookup for sendmail. Out ISP is Comast. If I turned off the DNS for sendmail, would Comcast flag our ip for spam?
The answer to question 1 really determines my next course of action and potentially more questions. As a general rule, do specific app questions like this belong in the CentOS forums?
Thanks!