I also now find groups.io to be not as good experience as Google Groups.

1) As noted by Marc, there is no way to see on UI that there are threads with new messages you didn't see. Here is the issue for that: https://groups.io/g/GroupManagersForum/topic/30886089
2) We found out that emails with numbers only in prefix (till `@`) are banned in groups.io . I.e. and email 12345<at>example.com cannot subscribe to groups.io

This is disappointing. I will raise those issues to see what options we have

Best regards,
Oleksandr Porunov