The issue here is not so much getting messages as spam, although that is the symptom of another problem.
The = sign is not part of his real address which is just his
username@....
Checking the subscriber list I find that his address is as above.
Somehow it gets added, probably by Groups.io.
Overnight, I asked him to delete himself, let me know, and I would Invite him.
Result is unknown at this time due to time zone difference.
Thanks,
Richard
