I’m sorry, Apple seems to be even more aggressive about classing our Discourse mailing list and the high reputation Amazon Simple Email Service as spam. Precisely zip I can do about it.
The frustrating this is that I cannot communicate this to the users concerned.
Discourse supports having a secondary email address which can be set in Preferences. That would be worth doing if people have an alternative email address.
I post these notices in the hope that the users in question may log in to the web interface from time to time.