> That's easy if you don't mind writing that file like this:
>
> user.gone@??? :fail: User gone, new address is user@???
> second.user@??? :fail: User gone, new address is private.address@???
>
> You can even add these two your existing aliases file. If you insist on
> a separate file, just add a second aliasfile director.
The intended Exim just relays mail for company.com being MX. So an
aliasfile would not be appropriate because the mail is not handled locally.