You need to use their e-mail addresses in the Pipex account format not their alias e.g. [email protected] not [email protected] Also you need to use the specific passwords for the account. These settings are available if you log onto Pipex using your master account details and go to the Control Panel.
If you are on Broadband the format might be something like abcd46%dsl.pipex.com with an 8 letter password.
Log on to Pipex and select Control Panel. Scroll down Control Panel and under the heading "My e-mail: Settings and support" you`ll see "Mailbox Administration" to the left. Below it is a small arrow icon ">" - Click that and your e-mail addresses and passwords will appear.