FreeBSD comes with Sendmail already
installed as the MTA which is in charge of
outgoing and incoming mail. However, the system administrator
can change the system's MTA. A wide choice
of alternative MTAs is available from the
mail category of the FreeBSD Ports
Collection.
Once a new MTA is installed, configure and test the new software before replacing Sendmail. Refer to the documentation of the new MTA for information on how to configure the software.
Once the new MTA is working, use the instructions in this section to disable Sendmail and configure FreeBSD to use the replacement MTA.
If Sendmail's outgoing mail service is disabled, it is important that it is replaced with an alternative mail delivery system. Otherwise, system functions such as periodic(8) will be unable to deliver their results by email. Many parts of the system expect a functional MTA. If applications continue to use Sendmail's binaries to try to send email after they are disabled, mail could go into an inactive Sendmail queue and never be delivered.
In order to completely disable
Sendmail, add or edit the following
lines in /etc/rc.conf:
sendmail_enable="NO" sendmail_submit_enable="NO" sendmail_outbound_enable="NO" sendmail_msp_queue_enable="NO"
To only disable Sendmail's
incoming mail service, use only this entry in
/etc/rc.conf:
sendmail_enable="NO"
More information on Sendmail's startup options is available in rc.sendmail(8).
When a new MTA is installed using the Ports Collection, its startup script is also installed and startup instructions are mentioned in its package message. Before starting the new MTA, stop the running Sendmail processes. This example stops all of these services, then starts the Postfix service:
#service sendmail stop#service postfix start
To start the replacement MTA at system
boot, add its configuration line to
/etc/rc.conf. This entry enables the
Postfix MTA:
postfix_enable="YES"
Some extra configuration is needed as
Sendmail is so ubiquitous that some
software assumes it is already installed and configured.
Check /etc/periodic.conf and make sure
that these values are set to NO. If this
file does not exist, create it with these entries:
daily_clean_hoststat_enable="NO" daily_status_mail_rejects_enable="NO" daily_status_include_submit_mailq="NO" daily_submit_queuerun="NO"
Some alternative MTAs provide their own
compatible implementations of the
Sendmail command-line interface in
order to facilitate using them as drop-in replacements for
Sendmail. However, some
MUAs may try to execute standard
Sendmail binaries instead of the
new MTA's binaries. FreeBSD uses
/etc/mail/mailer.conf to map the expected
Sendmail binaries to the location
of the new binaries. More information about this mapping can
be found in mailwrapper(8).
The default /etc/mail/mailer.conf
looks like this:
# $FreeBSD$
#
# Execute the "real" sendmail program, named /usr/libexec/sendmail/sendmail
#
sendmail /usr/libexec/sendmail/sendmail
send-mail /usr/libexec/sendmail/sendmail
mailq /usr/libexec/sendmail/sendmail
newaliases /usr/libexec/sendmail/sendmail
hoststat /usr/libexec/sendmail/sendmail
purgestat /usr/libexec/sendmail/sendmailWhen any of the commands listed on the left are run, the system actually executes the associated command shown on the right. This system makes it easy to change what binaries are executed when these default binaries are invoked.
Some MTAs, when installed using the Ports Collection, will prompt to update this file for the new binaries. For example, Postfix will update the file like this:
# # Execute the Postfix sendmail program, named /usr/local/sbin/sendmail # sendmail /usr/local/sbin/sendmail send-mail /usr/local/sbin/sendmail mailq /usr/local/sbin/sendmail newaliases /usr/local/sbin/sendmail
If the installation of the MTA does
not automatically update
/etc/mail/mailer.conf, edit this file in
a text editor so that it points to the new binaries. This
example points to the binaries installed by
mail/ssmtp:
sendmail /usr/local/sbin/ssmtp send-mail /usr/local/sbin/ssmtp mailq /usr/local/sbin/ssmtp newaliases /usr/local/sbin/ssmtp hoststat /usr/bin/true purgestat /usr/bin/true
Once everything is configured, it is recommended to reboot the system. Rebooting provides the opportunity to ensure that the system is correctly configured to start the new MTA automatically on boot.
All FreeBSD documents are available for download at https://download.freebsd.org/ftp/doc/
Questions that are not answered by the
documentation may be
sent to <freebsd-questions@FreeBSD.org>.
Send questions about this document to <freebsd-doc@FreeBSD.org>.