Am Samstag, den 05.09.2015, 12:29 +0200 schrieb Mail Delivery System:
 This is the mail system at host srv15.ffnw.de.

 I'm sorry to have to inform you that your message could not
 be delivered to one or more recipients. It's attached below.

 For further assistance, please send mail to postmaster.

 If you do so, please include this problem report. You can
 delete your own text from the attached returned message.

                    The mail system

 <core@freifunk-ol.de>: host srv01.ffnw.de[37.120.176.207] said: 550
 5.1.1
     <core@freifunk-ol.de>: Recipient address rejected: User unknown
 in virtual
     mailbox table (in reply to RCPT
TO command)

Meh, wo fliegt der alte Kram denn noch rum?