Mmmm. That's might also be a solution, but if I forward all the mails, don't they all originate from my own secondary email address then? If that is the case, that's something I wouldn't really want...

On the other hand, that's looking for a solution for something that shouldn't be a problem. I mean, I've got the very same setup working flawlessly here with my own email addresses. I would really like to know why it doesn't work this time...