Determine which MTA is being used on the system

Reviewer: name contact BSD flavour

Concept

Recognize the role of the MTA, recognize which MTA(s) are available during each BSD's operating system install routine and which configuration file indicates the MTA(((MTA))) in use on the system. Recognize the difference between the mbox(((mbox))) or maildir(((maildir))) mail destination file format type.

Introduction

By default, the BSD systems have mail transfer agent (MTA) enabled for at least handling mails sent from the local machine.

FreeBSD, OpenBSD, and DragonFly include Sendmail in their base installs. NetBSD includes Postfix. (TODO: FOOTNOTE: Older versions of NetBSD included both Sendmail and Postfix.)

Third-party MTA alternatives or sendmail replacements are available through the package collections, such as Exim, Qmail (not included in OpenBSD's ports), Postfix and many others.

Selecting the MTA can be done by configuring the mailer.conf configuration used by the mailwrapper tool. The BSD's default /usr/sbin/sendmail (TODO: what about /usr/lib/sendmail) is really a symlink to /usr/sbin/mailwrapper. This uses /etc/mail/mailer.conf (or /etc/mailer.conf on NetBSD) to define common replacement programs.

TODO: for example

TODO: show how can be tested

TODO: note that this BSDA doesn't teach how to configure a mail server, but TODO: briefly cover how to turn on and off and how to disable at boot and where logs are at TODO: point to other sections for details