SOLVED Failed Emails Max Reached

See this post Domain example.com has exceeded the max defers and failures per hour (5/5

And this is the page of the documentation that explains everything: Tweak Settings - Mail - Version 68 Documentation - cPanel Documentation

and also How to Prevent Spam with Mail Limiting Features - cPanel Knowledge Base - cPanel Documentation

 

Just adding a note that may be of use, one of our clients called us today with this issue.

It turned out that they had forwarders set up to redirect emails for their business domain name to their various Gmail accounts. What was happening is a burst of junk emails was coming in and being forwarded to Gmail. Google however noticed too much junk was being relayed by our mail exchange thus started deferring the messages.

What this suggests is that your mail exchange within WHM is correctly limiting outbound emails to help maintain a good reputation amongst other mail exchanges. If it didn't do this and you continuously bombarded junk to Gmail they would eventually block your mail exchange long term, which I'm sure your other customers won't like one bit. Therefore this setting should be very on.

The issue seems to correct itself within the hour. You should also check the outbound mail reports for the domain name in question to find where the junk is coming from, as you perhaps need to blacklist a malicious mail exchange delivering it to your mail exchange.