Domain has exceeded the max defers and failures per hour (5/5 (100%)) allowed

Are you seeing this error in your mail logs? Chances are your client has triggered a fail safe in Exim that restricts them from sending any email out of your server. This event is triggered when an account sends email to addresses that fail or defer more than the set limit. So for example, an account sends out 10 emails in one hour. 5 of these messages are to addresses that fail or defer and the other 5 deliver ok. That means that this accounts fail/defer percentage per hour is 50%. If your limit set within the WHM is 50% or lower mail will now be rejected when that account sends more email.

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

  1. Ensure your account is not sending spam. Check your mail delivery reports from your cPanel Track Delivery option. 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 to check whether the devices are infected.
  2. Check autoresponders and spam filters. This block can sometimes be triggered when you have an autoresponder setup 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.
  3. Check your mailing lists is up to date. If you are sending a mass marketing email, please check your mailing list is up to date by removing email addresses which 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.


Here’s how you can change the threshold or disable this feature!

  1. Log into the WHM as root
  2. Click tweak settings
  3. Click the Mail tab
  4. Scroll down and find the “Maximum percentage of failed or deferred messages a domain may send per hour” setting
  5. Change the % or you can disable this feature by selecting the Unlimited option