This is a problem after upgrading to 'stretch' which is the 'stable' release now.
Dovecot starts before the network is up. i used a modified fix from RH: https://bugzilla.redhat.com/show_bug.cgi?id=1309946 What works for me in debian stretch: create file /etc/systemd/system/dovecot.service with the content ~~~~~~~~~~ .include /lib/systemd/system/dovecot.service [Unit] After=network-online.target ~~~~~~~~~~
