Andrus,
I think you just have to have the right Username/Password. But I don't have the slightest idea though to tell you where to find it in Exchange. I think you can set up a specific profile though and use that from your MAPI automation process.
>with oleMAPISession
> .UserName = 'User'
> .Password = ''
> .Signon()
>
>This produces an message Incorrect profile and produces Exchange profile dialog and fails. If OE is default MAPI client, this works.
>How I can send e-mail with OE if it is not default mapi client?