Amazon Sellernotifications are eaten by postfix plesk_virtual

[turbomettwurst]

Hello Humble Sirs and Ladies,
I have a somewhat bizarre problem with postfix, namely the plesk_virtual transport.
A Customer of mine sells via Amazon and whenever an Item is sold Amazon sends you an email. These Messages are lost. Strangely enough the problem is limited to Seller Notifications, all the other E-Mails sent by Amazon are delivered to the customers mailbox.
The E-Mail Address Amazon is sending to ([email protected]) is an alias of [email protected].

I have enabled verbose logging for the pipe transport in master.cf

plesk_virtual unix - n n - - pipe -v flags=DORhu user=popuseropuser argv=/usr/lib64/plesk-9.0/postfix-local -f ${sender} -d ${recipient} -p /var/qmail/mailnames

Unfortunately that didn't seem to help in diagnosing the problem, the way I see it the problem lies somewhere within argv=/usr/lib64/plesk-9.0/postfix-local which is unfortunately a blob and doesn't seem to support verbose logging of any kind...
The Verbose Logfile is attached. Any Pointers would be greatly appreciated...