I've had an odd problem with some forum-initiated emails bouncing claiming we're (our mail server) on a blocklist, despite checks that find us on no blocklists...
Turned out, the bounces were happening due to a badly formatted SPF record in our DNS which has been corrected.
I've done a 'remind' to all the waiting for validation new members, so hopefully they'll see the email (instead of me seeing a bounce).
Reminder.. check your spam folder for messages -- some email services put messages from wxforum.net there.