Create users and groups without password .

[Kostas Sfakiotakis]

How can someon create a user and a coresponding group without any
password . The user isn't needed to have a shell even .
Examples for such a case would be user amavis and smrsh , both
needed with a sendmail installation  the former in order to intergrate
sendmail with amavis for virus checking and the later of course is the
sendmail secure shell ?

Regards ,
   Kostas