Well, I'm very grateful for your fast response.
But, fetchmail is one of installation conditions, isn't?
Do you want to say more setup conditions on existing installation?
No, not all of my users have e-mail account on external system, but part of them. All of them have internal account, and part of them are externally.
Oficcially.

))
My problem is how to explain exsistence two domens.
Idea is unique account.
But how to do it? Your proposal isn't clear to me.
With regards, rrad.
PS. Excuse on my English, I'm not nature.