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

[hoZt]

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!