Ahh hang on. I'm talking rubbish. This is the actual posts not the users. I'll have another think!!
EDIT:
It's actually quite difficult to do, as the code doesn't (seem to) note which users have been sent the message. It's all or nothing.
General help
Splitting Mail to avoid server/host limits
Denne diskusjonen har blitt stengt, og du kan derfor ikke svare i den lengre.