Thanx for your help phoenix, but take a look at my first post: It works fine when using
alias domains and it will probably work fine when using an alias in the alias2.com/alias1.com domain. The only situation where this alias domains might get you into troubles is when you have one catchall for multiple domains and different local users on each domain -- which is a quite unusual configuration, isn't it?
I just wanted to point out that this behavior is a bit strange and maybe somebody at Zimbra should write a PostIT for Zimbra 10.0 that the catchall-setting should be a setting for the domain and not for an account.