sudo ln -s /usr/local/Cellar/mysql/5.6.25/lib/libmysqlclient.18.dylib /usr/local/lib/libmysqlclient.18.dylib

shown by error

Jul 3 09:46:08 zeus dovecot[2223]: imap-login: Disconnected (disconnected before auth was ready, waited 24 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, TLS: Disconnected, session= Jul 3 09:46:14 zeus dovecot[2223]: auth: Error: dyld: Library not loaded: /usr/local/lib/libmysqlclient.18.dylib Jul 3 09:46:14 zeus dovecot[2223]: auth: Error: Referenced from: /usr/local/libexec/dovecot/auth Jul 3 09:46:14 zeus dovecot[2223]: auth: Error: Reason: image not found Jul 3 09:46:14 zeus dovecot[2223]: auth: Fatal: master: service(auth): child 44250 killed with signal 6 (core dumps disabled) Jul 3 09:46:14 zeus dovecot[112]: master: Error: service(auth): command startup failed, throttling for 60 secs

Somewhere along the line, the link got removed ? Watch out for updates

Robert Chalmers https://robert-chalmers.uk author@robert-chalmers.uk @R_A_Chalmers