Seems that Swisscom/bluewin's mail servers are blocking each other again, same problem happened on February 14.

Generierender Server: zhhdzmsp-smtp12.bluewin.ch

 

xxx.yyy@bluemail.ch
mxbw.bluewin.ch #<mxbw.bluewin.ch #5.0.0 smtp; 554 IP: 195.186.136.31, You are not allowed to send us mail. Please see http://www.dnsbl.manitu.net/lookup.php?value=195.186.136.31 if you feel this is in error.> #SMTP#