Hello everybody
Since yesterday, we see a lot of bounced messages to bluewin addresses with SMTP code 554, for example: relay=mxbw-bluewin-ch.hdb-cs04.ellb.ch[195.186.227.50]:25, delay=0.16, delays=0/0.01/0.09/0.05, dsn=5.2.0, status=bounced (host mxbw-bluewin-ch.hdb-cs04.ellb.ch[195.186.227.50] said: 554 5.2.0 sc976: Rejected due to policy reasons - https://support.bluewin.ch/provider/bounce/XXXXXXXXXXXXXXXXX%5Bredacted%5D== (in reply to end of DATA command)) Unfortunately, sc976 is not documented on https://postmaster.bluewin.ch/content/de/technical-details/ We can't see any general pattern behind those rejections (hosts trough our entire IP range are affected), switching to a different IP address for delivery works in most cases.
Do you see the same and have any insight what is going on here?
Greetings Peter