forward mails get no error

Hi,

I have a problem with forward mails.

Following example.

Email: test1@plesktest.abc (My adress in plesk)
Email: max@muster.abc (the forward adress insert in test1@plesktest.abc)
Email: sender@domain.abc (sender adress)

If I send a mail from sender@domain.abc to test1@plesktest.abc
Every thing is fine and max@muster.abc get the mail

But now if i change the adress...

forward mails get no error