Today wanted to test a user and password of a e-mail if are correct .
So to do that
/usr/sbin/authtest account@domain.com ‘password’
Returned
Authenticated: module authvchkpw
Home directory: /home/vpopmail/domains/domain.com/account
UID/GID: 7797/2109
AUTHADDR=account@domain.com
AUTHFULLNAME=account
OPTIONS=<none>