alefattorini
....it should be possible to redirect admin@ to any other user or address, but on SME server there is no way out.
You can redirect or forward all admin mail to any user you specify in server manager user panel.
Perhaps what you meant to say, was that all root type system mail should be able to be redirected to any user address specified, other than admin, and that the admin email address can be used for any other purpose.
I am sure that could be done if someone was willing to fund the development work.
The developers do not think this is a significant issue that requires their freely given time to fix, but paying them to do so would certainly speed up the process. Same rules apply in most distros.
You should try some alternative 
There are usable workarounds given here, so trying an alternative (I assume you mean distro) is not really necessary.