"Max Defers" refers to part of an error message that appears when an email fails to send via mail hosting. An example of the full message is:
"Domain has exceeded the max defers and failures per hour (5/5 (14%)) allowed."
This message means that email delivery attempts have failed, and the messages could not reach the intended recipients.
Several factors can cause this issue, including:
The recipient’s email address is invalid (e.g., due to a typo)
The destination email domain’s MX records cannot be found
Anti-spam protection features are triggered due to repeated failed attempts
The last point refers to how cPanel automatically blocks accounts that send multiple invalid emails within a short time frame. This behavior may be interpreted as spam activity, leading to the Max Defers message as a preventive measure.
In some cases, users may encounter a Max Defers error even though there was no intention to send spam. Upon review, it is often found that the issue was caused by a mistyped email address. Multiple delivery attempts to the incorrect address can lead to deferrals, eventually triggering the error message.
To check the root cause of the issue, follow these steps:
Login to your cPanel
In the search bar at the top, type “Track Delivery” and select the matching result from the list.
The report will appear in the table below. The contents of the table can also be filtered as needed. If you only want to display emails that failed to be sent, click Show Failures checkbox.
Here is an example of a report showing emails that failed to send. Based on this report, there are several things you can pay attention to, including:
Recipient - Ensure that the recipient address is correct
Result - This column will describe the reason why the email failed to send.
Error Code - You can check the meaning of the code at this link
Meanwhile, here is an example of a report showing deferred emails. You can do the same as the previous step. In the Result column, there is an Error Code : 451 Internal resource temporarily unavailable .
After checking the error code and what it means on the list, from our example it means:
451 | Internal resource temporarily unavailable
Description: The sending mail server is subjected to Greylisting. This requires the server retries the connection, between one minute and 12 hours. Alternatively, the sender's IP address has a poor reputation.
Recommended Resolution: These reputation checks can be bypassed with an Auto Allow or Permitted Senders policy. If it's legitimate traffic, modify your Greylisting policy.
Message Delivery Status on Track Delivery
The following icons indicate the delivery status of your email messages:
Icon | Meaning |
 | The system has successfully delivered the message. |
 | Message status is unknown, or delivery is in progress. |
 | The system has delayed the message. |
 | Message encountered a delivery error. |
 | The system has archived the message. |
 | The system rejected and deleted the message due to Simple Mail Transfer Protocol (SMTP) issues. This may happen if the sending server does not use secure configuration or is listed on the Real-time Blackhole List (RBL). |
 | The email server accepted the message but did not deliver it to the recipient's inbox. This can happen when the recipient's software or email filters block the message. |
Now that you know the possible causes of the error message when sending emails via mail hosting, you can use the Track Delivery tool in cPanel to review email activity and identify appropriate solutions based on the recommended resolution of the error code.