As pointed out by Daniel, the original issue was caused by a listing of this IP on Spamhaus SBL and Bluewin does in fact use Spamhaus as a RBL provider and has done so for quite some time. As to the "DNSNULL" part of the error message, this was caused by an issue in the lookup of the appropriate delisting URL. The request in question has been fixed now and will provide proper answers again.
Sorry for the inconvenience.
Cheers Marcel
From: swinog-bounces@lists.swinog.ch swinog-bounces@lists.swinog.ch On Behalf Of Andreas Fink Sent: Donnerstag, 11. Juli 2019 11:33 To: swinog@swinog.ch Subject: [swinog] bluewin & DNSNULL
Does any one have a clue what DNSNULL means in the following context of a mail delivery error?
<....@bluewin.chmailto:claudine.beaud@bluewin.ch> (mx-v02.bluewin.chhttp://mx-v02.bluewin.ch: 554 mxbw.lb.bluewin.chhttp://mxbw.lb.bluewin.ch vim dzmsp-mxin12.bluewin.chhttp://dzmsp-mxin12.bluewin.ch Swisscom AG IP: 79.134.251.203, You are not allowed to send us mail. Please see DNSNULL if you feel this is in error)Reporting-MTA: dns; mail.fink.orghttp://mail.fink.org Arrival-Date: Thu, 11 Jul 2019 11:19:58 +0200 ...
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