XF 1.3 Email Suddenly Stopped

On Tuesday I stopped receiving email notifications from the board. Nothing has changed, same server, same host, no changes to email system. The only thing I can think of is I ran acp > tool > clean up permissions on Tuesday. Perhaps I using another cache cleaning tool as well on that day, not sure. Anyone have any suggestions on how to diagnose the issue.
looks like it may be a DNS issue on my server... .still confirming. Installed [BD] Mails to use a 3rd party smtp server to see if that fixes the issue.