Unless you have root on the machine, adduser won't work. And passwd doesn't accept a password on the command line (it would be a huge security breach if it did), you'll have to use Expect;

As for the rest of your questions, they depend on the details of how the server was set up, and this is not the place to discuss them. You want a unix discussion forum. Go back two routers and turn left.

And passwd doesn't accept a password on the command line (it would be a huge security breach if it did), you'll have to use Expect;

That is not actually correct. For example you can (as root) do:

sub add_shell_passwd {
    my ( $user, $shellpwd ) = @_;
    open PWD, "|$PASSWD_BIN --stdin $user" or die "Can't open pipe to 
+$PASSWD_BIN $!\n";
    print PWD $shellpwd, "\n";
    close PWD;
}
[download]

On the other hand adding a shell password adds a full shell account for the user. For the benefit of the OP there are many ways to skin this cat. If you want to make real user accounts you either want to make /dev/null the users default shell (so they can't login) or use say cram-md5 so they can have a pop3 pwd but no shell password. This is typically NOT what you want to do. Try Googling for 'creating virtual pop3 accounts linux'

cheers

tachyon

That is not actually correct.
Actually, it IS.

The passwd manpage on Linux (Debian) and Solaris do not list the --stdin switch. Quite possibly you are running some system that supports it, but that DOES NOT make what I said incorrect.

The question did not define which operating system the machine he is using actually runs, but it's far more likely that it doesn't support --stdin that that it does.