Ah, thank you mmorse...
Yeah, I decided to do something crazy and experiment a whole heck of a lot.
Quite a learning experience in the end.
I still wonder why all the accounts I had was not detected, though, but at least I'm up and running again (and with my latest tweaks (which I thought I had done - but missed the alias part) I now get the mail people send to me
).
Zimbra is pretty complex, but also a very nice piece of groupware...