Does any one have a clue what DNSNULL means in the following context of a mail delivery error?




 <....@bluewin.ch> (mx-v02.bluewin.ch: 554 mxbw.lb.bluewin.ch vim
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.org
Arrival-Date: Thu, 11 Jul 2019 11:19:58 +0200

...




Andreas Fink
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