Perhaps you'd be better off without the virtual mailboxes anyway?
Perhaps, and that's where i actually started from. Virtual users are an attractive feature tough and as it didn't seem too intimidating, i thought i could give it a try. 6 hours later, i was wiser.
Virtual mailboxes have their place, indeed, but more so for large numbers of domains and users. For a small-timer (as it sounds like you are), I wouldn't say they're attractive. Increased complexity, decreased functionality, [usually] security tradeoffs. (System users who own all and ONLY their own mail are not going to endanger others' mail. Virtual mailboxes typically are owned by a shared UID+GID, and a compromise of that UID or GID could threaten all mail.)
Rob, thank you for your comments! I'll just stay with system users then, i only need a few accounts as you guessed correctly. Virtual users appeared nice due to the separation from the system. But probably not worth the effort, as you argumented.
Cheers, Christian