After grappling for a couple of years with issues getting email successfully delivered to some domains (like yahoo and hotmail), I'm now paying for a commercial email service to take care of email delivery. This seems to have been successful, and I can see the email is now getting thru.

So...you may find you've now started getting emails for thread subscriptions etc, which you were never getting in the past. New users should hopefully have more success registering and activating their accounts etc.