For the reasons behind why I needed to find out what my MTA was, you should check out this post detailing an error that occurred with qmail – “CNAME lookup failed temporarily. (#4.4.3) I’m not going to try again; this message has been in the queue too long.”
A quick snippet of information for those looking to find their active mail transfer agent is to issue, as a privileged user, this command at the terminal:
root@mail ~# alternatives --display mta
Which should yield something similar to the following output:
mta - status is manual.
link currently points to /var/qmail/bin/sendmail
/var/qmail/bin/sendmail - priority 100
slave mta-pam: (null)
slave mta-mailq: (null)
slave mta-newaliases: (null)
slave mta-rmail: (null)
slave mta-in_libdir: /var/qmail/bin/sendmail
slave mta-mailqman: (null)
slave mta-newaliasesman: (null)
slave mta-aliasesman: (null)
slave mta-sendmailman: (null)
/usr/sbin/sendmail.postfix - priority 30
slave mta-pam: /etc/pam.d/smtp.postfix
slave mta-mailq: /usr/bin/mailq.postfix
slave mta-newaliases: /usr/bin/newaliases.postfix
slave mta-rmail: /usr/bin/rmail.postfix
slave mta-in_libdir: (null)
slave mta-mailqman: /usr/share/man/man1/mailq.postfix.1.gz
slave mta-newaliasesman: /usr/share/man/man1/newaliases.postfix.1.gz
slave mta-aliasesman: /usr/share/man/man5/aliases.postfix.5.gz
slave mta-sendmailman: /usr/share/man/man1/sendmail.postfix.1.gz
Current `best' version is /var/qmail/bin/sendmail.
What did we just run?
Alternatives, in its most basic form will let you know information about all the different symbolic links that you specify. alternatives and its usage can be more accurately defined by its man page on:
alternatives creates, removes, maintains and displays information about the symbolic links comprising the alternatives system. The alternatives system is a reimplementation of the Debian alternatives system. It was rewritten primarily to remove the dependence on perl; it is intended to be a drop in replacement for Debian’s update-dependencies script. This man page is a slightly modified version of the man page from the Debian project.
It is possible for several programs fulfilling the same or similar functions to be installed on a single system at the same time. For example, many systems have several text editors installed at once. This gives choice to the users of a system, allowing each to use a different editor, if desired, but makes it difficult for a program to make a good choice of editor to invoke if the user has not specified a particular preference.