To use postfix instead of sendmail:
  - clear sendmail queue and stop the sendmail daemons

Run the following commands to enable postfix during startup:
  - sysrc postfix_enable="YES"
  - sysrc sendmail_enable="NONE"

If postfix is *not* already activated in %%MC_PREFIX%%/etc/mail/mailer.conf
  - mv %%MC_PREFIX%%/etc/mail/mailer.conf %%MC_PREFIX%%/etc/mail/mailer.conf.old
  - install -m 0644 %%DATADIR%%/mailer.conf.postfix %%MC_PREFIX%%/etc/mail/mailer.conf

Disable sendmail(8) specific tasks,
add the following lines to /etc/periodic.conf(.local):
  daily_clean_hoststat_enable="NO"
  daily_status_mail_rejects_enable="NO"
  daily_status_include_submit_mailq="NO"
  daily_submit_queuerun="NO"

If you are using SASL, you need to make sure that postfix has access to read
the sasldb file.  This is accomplished by adding postfix to group mail and
making the %%PREFIX%%/etc/sasldb* file(s) readable by group mail (this should
be the default for new installs).

If you are upgrading from prior postfix version, review the RELEASE_NOTES to
familiarize yourself with new features and incompatabilities.