PREUN
/bin/sh
if [ $1 = 0 ]; then update-alternatives --remove sendmail-command /usr/bin/msmtp fi
POSTIN
/bin/sh
update-alternatives \ --install /usr/sbin/sendmail sendmail-command /usr/bin/msmtp 5 \ --slave /usr/lib/sendmail sendmail-command-in_libdir /usr/bin/msmtp