Functions of ppsw

Virtual mail domains
@cam.ac.uk
managed mail domains

Mailing list distribution
@lists.cam.ac.uk

Directing messages to hubbed servers
e.g. @cus, @hermes, @mole.bio

Outgoing mail relay ("smarthost")
for users and hubbed servers

Backup mail receiver for non-hubbed servers
e.g. @cup, @damtp, @esc, @jesus, @newton