I'd made a fresh installation and the user for dovecot can't acces the imscp database.
After some testing i found out that the problem was the password which contains some chars which let the dovecot user not access the database over the dovecot daemon ()
The password which was generated:
The access to mysql on shh shell works perfect, but not over the dovecot daemon. After changing the password (without ^) the dovecot worker can connect successfully.
Can you please check this. Maybe some chars will not work.