Mac OS X in a Nutshell

Mail Services

Email-related daemons can be put into two categories: mail transport agents (MTAs), which send new email messages to their destination machines, and mail delivery agents (MDAs), which send mail that’s landed in a user’s mailbox to that user’s personal computer.

Mail Transport Agents (sendmail)

A mail transport agent sends email to other computers, most often via the SMTP protocol. Mac OS X ships with sendmail , the most common mail-serving program on the Internet.

Tip

Run sendmail only if you need to provide mail-sending services to yourself or your network. You don’t need to run this service to simply send email, so long as there is an SMTP server that will accept connections from your machine; most ISPs provide mail services on their own servers, for example.

Using sendmail

Mac OS X has no easy interface for running sendmail as a daemon, but it doesn’t take too much work to get it going, since most of the setup has already been done for you. Just edit /etc/hostconfig, changing the line MAILSERVER=-NO- to MAILSERVER=-YES-. This line is read by the startup script at /System/Library/StartupItems/Sendmail/Sendmail, which cleans up the mail queue and starts the sendmail daemon by issuing the command sendmail -bd -q1h. See Section 13.8 later in this chapter for more information on how this works. When you restart the machine, sendmail should start along with it. (You can also test it by simply running the script from the command line.)

From there, sendmail runs quite ...