[Dovecot] Plus sign in usernames: user+domain.com?

I am migrating from a cpanel server that has usernames in the format "user+domain.com". On the new server I am using the format "user.domain.com" and it all works perfectly with dovecot / postfix. Is there any way that I can allow users to login either with the "." or "+" delimiter?

Thanks in advance for any suggestions!