Well the obvious answer would be that PBEM isnt actually officially supported by Activision in CTP2...
It is available though, search for a thread here by Mr Ogre, about how to find this "hidden" feature. Be warned, it is very buggy, and there is no built in human-human diplomacy. (Locutus is looking at a mod to do this though)
Because of the lack of human-human diplomacy, it is not as good as CTP2 MP, but there are also I believe problems with that, and *.tga loading problems, resynchronisation bugs...
Basically, Activision did not see MP as a major part of CTP2, and so the entire engine performs very poorly.
Sorry to have to say this, but as far as MP goes, stick with CTP1. Play single player if you like CTP2, or join a succession game, and at least there is some contact with other players.
Not to be totally pessimistic though, MP is played a bit, and there haven't been too many people posting MP complaints here, and I'm sure that any more people trying to get human-human diplomacy via SLIC would be welcome if they can be bothered to try
