FYI

-------- Forwarded Message --------
Subject: Delayed Mail (still being retried)
Date: Fri, 23 Sep 2016 03:19:16 +0200 (CEST)
From: Mail Delivery System <MAILER-DAEMON@comu.ring0.de>
To: tarek@ring0.de

This is the mail system at host ring0.de.

####################################################################
# THIS IS A WARNING ONLY.  YOU DO NOT NEED TO RESEND YOUR MESSAGE. #
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Your message could not be delivered for more than 4 hour(s).
It will be retried until it is 5 day(s) old.

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

<support@nordwest.freifunk.net>:
host srv01.ffnw.de[37.120.176.207] said: 454
    4.7.1 <support@nordwest.freifunk.net>: Relay access denied (in reply to
    RCPT TO command)