Shaw Communications Inc. and their mail filtering sub-contractor (Cloudfilter/Cloudmark) are again delaying, and now even bouncing, email sent to shaw.ca addresses. However, we have no way of communicating with Shaw mail server admins, so we cannot talk to them about how their filtering practices are non-standard and unpredictable.
Our mail server is still/again not in any of the 250 major blacklists that we monitor, so it is unclear why Shaw/Cloudfilter are causing this problem. If you are a Shaw customer, we strongly recommend that you contact Shaw and complain. We also recommend that you do not forward your email to any addresses on their domain.
Update, 2021-07-13 15:45 (PDT): Bounce messages will contain this line, or something very similar to it:
host shw-central.mx.a.cloudfilter.net[3.96.81.40] refused to talk to me: 421 shw-ibgw-4001a.ext.cloudfilter.net cmsmtp too many sessions from 178.62.195.26 AUP#CNCT
Normally bounce messages can be easily deciphered, but even we don’t know what this means or how it makes any sense.
