Outgoing mail from any machine will give this return address. To send mail withing the group, use just the username . To read or send mail, the Sun mailtool is highly recommended for its graphical interface. Or you can brave the unix mail command.
Mail reading on the other machines is flaky.
The bad news is that at present there is no way to give a forwarding address and it will go to your mainframe account, if you have one. Test before you go to be sure mail won't bounce.