Something happened after I updated your plugins and now all the emails coming from the site is not working. Hence, no one can join. Please let me know how to troubleshoot. Thanks.
FYI - I checked with host and nothing happened on my server.
The most of email sending issues are server and site specific issues so we can't help in these cases. We have a good list for website admins to find the reason and fix it. please read this FAQ post: