I am by no means an expert, but people here are trying to help me out so I thought I would reciprocate..at least I can try..
(I'll try NOT to be wrong, but no promises.. hehe)
Looks like 2 errors
1) Fatal: execv(/usr/lib/dovecot/managesieve) failed: Permission denied
ls -l /usr/lib/dovecot/managesieve
(I think dovecot might need to be owner and have +x permissions..but get the "ls -l" results first..)
2) Fatal: Invalid configuration in /etc/dovecot/dovecot.conf
can you post your /etc/dovecot/dovecot.conf ?