When you get an error similar to "Domain yourdomain.com has exceeded the max defers and failures per hour (10/10 (100%)) allowed" in an email return, it means outgoing emails from your domain have triggered a rule in the server that will prevent any further outgoing messages from being sent. This happens when a domain account sends emails that fail or are delayed by the recipients mail server.
You can find out the cause of this error message by using the "Track delivery" tool in your cPanel account. Clicking on the Track Delivery icon will retrieve data for all email traffic, and as you cycle through it, you should see groups of bounced messages that can help you determine which sender caused the problem and why. Failures can come in the form of unknown user to too many connections from your IP.
If the number of failures or postponements exceeds the server limit, the domain sending the emails will not be able to send any further messages externally until one hour has passed since the first failure .
This can occur under several circumstances:
- When you send messages and this happens, it probably means that some of your mailing list subscribers are no longer using the email addresses they subscribed to. You will need to clean up your email database and stop sending emails to these inactive accounts.
The "Track Delivery" tool in your cPanel helps you identify inactive emails for cleaning and updating your database.
- When you do not send a mailing but you receive the return message, it may mean that your account has been hacked. Follow the previous steps to locate recently sent messages from your account.
If you don't recognize most of the email addresses in the Track Delivery report, you need to update the password for the email account used to send those emails.
You should also put a captcha on the submission forms on your site if you have one.
- If the recipient mail server rejects your messages, at this time, your correspondent must contact his service provider to verify the cause of this blocking. In the meantime, you should stop sending to this recipient.