2. Click the 'New...' button under the 'E-Mail' tab.
3. Click on 'Manual setup or additional server types' and hit Next.
4. Click 'POP or IMAP' and hit Next.
5. Fill in your information here. The incoming mail server must be 'mail.aa.net.uk' and the outgoing mail server must be 'smtp.aa.net.uk'. Once done, hit the 'More settings...' Button on the bottom right of the window.
6. In the 'Outgoing Server' tab, tick 'My outgoing server (SMTP) requires authentication. Make suer 'Use same settings as my incoming mail server' is selected.
7. In the 'Advanced' tab, set the incoming server to 993 for IMAP, or 995 for POP3 - the encryption type must be SSL. Set the outgoing server to 25 - the encryption type must be TLS.
8. Hit Done and test the account settings. Everything should now work.