How to configure Dovecot user login to use full domain email
Dovecot is an open-source IMAP and POP3 server for Linux/UNIX-like systems.
By default userids in dovecot using passdb doesn't include the domain name.
Eg: username instead of username@domainname
To make the users to use the format username@domainname,
Open the dovecot configuration file /etc/dovecot/conf.d/10-auth.conf and update the below line,
auth_username_format=%n
That's all...