What is this error?
If you are receiving an error like "Domain example.com has exceeded the max defers and failures per hour (5/5 (100%)) allowed" in an email bounce back, it means that an outgoing email from your domain has triggered a rule in the server that will stop any further email from going out of the server. This happens when a domain account sends out emails that either fail or get deferred. If the number of failures or defers is greater than the server limit, no further emails are allowed.
How can I fix this?
This error is derived from an hourly monitoring system, where any blocked domains are allowed to send emails again at the top of every hour. For example, if you received this error at 2:45 pm, the block would release at 3:00 pm and the domain will be able to send emails out once more.