This is the mail system at host mail.zapf.in. 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 <mail(a)fabianfreyer.de&gt;: host ASPMX.L.GOOGLE.COM[74.125.128.26] said: 550-5.7.1 [94.130.65.175] Our system has detected that this message is not RFC 550-5.7.1 5322 compliant: 550-5.7.1 'From' header is missing. 550-5.7.1 To reduce the amount of spam sent to Gmail, this message has been 550-5.7.1 blocked. Please visit 550-5.7.1 https://support.google.com/mail/?p=RfcMessageNonCompliant and review 550 5.7.1 RFC 5322 specifications for more information. ji18-20020a170907981200b0098e19ebc8fcsi884021ejc.679 - gsmtp (in reply to end of DATA command)