How to resolve domain has exceeded the max defers and failures per hour error?

Problem

When you send an email, the following error can occur:
Domain example.com has exceeded the max defers and failures per hour (10/10 (100%)) allowed. Message discarded.

Cause

Your account has exceeded the allowed number of bounced messages per hour and as a result, your sending rights have been blocked.

This block is required to prevent your account and our server’s IP from being permanently blocked by third party mail servers and spam blacklist.

Resolution

The block will be automatically removed on the hour. Please wait till an hour has passed to attempt to send an email again.

Prevention

To prevent max defers and failures per hour error messages please check the following:

• Ensure your account is not sending spam. Check your mail delivery reports in your cPanel > Track Delivery. If you see a large number of delivery failures from one of your email addresses then we recommend immediately changing your mailbox password and virus scanning all your devices.
• Check autoresponders and spam filters. This block can sometimes be triggered when you have an autoresponder set up to send an out-of-office reply to all emails you receive. This is because the autoresponder will reply to all emails including spam email addresses which do not exist. In these cases, the reply will fail which counts towards the delivery failure count per hour on your domain. To resolve this ensure your Spam Filters are enabled on your cPanel account. This will ensure emails we flag as spam is not sent an autoresponse.
• Check your mailing lists are up to date. If you are sending a mass marketing email, please check your mailing list is up to date by removing email addresses that no longer work. Sending to multiple invalid email addresses will trigger the block. The only way to resolve this is to clean your mail list and remove email addresses which result in bouncebacks.