What is the function of the /etc/mail/mailertable file?
 

I have recently started at a company after the old Linux admin left over a year ago, I have been tasked to get the Linux servers up to date. One of the first things I looked into was to get root mail working so I could better monitor what was going on, the sendmail file has never been setup or any of the other files in /etc/mail except the mailertable file which has the following entries: "mydomain.com smtp:mail.mydomain.com"(mydomain substituted for actual), not sure what this file is doing? some mail is going out, a clamav log file, but nothig else else I can see.

The "mailertable" feature enables manual routing of mail. The /etc/mail/mailertable file will contain instructions about how and where to forward mail for specific domains. The entrysimply routes mail for the "mydomain.com" domain to "mail.mydomain.com", overriding any MX records.

You could also forward mail to an SMTP service on a different host and/or port, or you could specify that mail should be transfered using another protocol, like UUCP.