In simple terms, email defer is where the system starts rejecting outgoing email instead of queuing it once a user reaches the maximum allowed emails per hour.
Usually this event is triggered when an account sends email to addresses that fail or defer more than the set limit.
The "exceeded the max defers and failures per hour" message is a cPanel message that outgoing email is being held on the server until the number of emails that have failed or been deferred is below the email threshold.
In Exabytes shared hosting, the maximum defer limit shall be 30 .
The domain users are only able to send out the emails after 1 hour of blocking period.
Once the defer error has exceeded this limit 30, the below exception will be thrown:
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
Domain thedomain.com has exceeded the max defers and failures per hour (30/30 (100%)) allowed. Message discarded.
Possible Cause and Solution
1. The email address has been compromised to send out spam emails
If the user is experiencing the defer limit issue caused by compromised email accounts, we recommend changing the email password to stronger characters with at least 18 characters inclusive of upper and lower case letters, numbers and symbols .
In addition, may also scan the computer with updated antivirus to remove any malware, adware, spyware, rootkits, trojans, etc.
If the issue still persists and if the user uses an email application such as Microsoft Outlook or Thunderbird, user can temporarily disable the mail app to stop sending email from the email application.
Meanwhile, user can use webmail to send & receive emails.
2. Bulk email sending (intentionally)
If the users experiencing the defer limit issue caused by intentionally sending out mass mailing/bulk emails for marketing purposes, may consider subscribing to an Email Marketing Service such as EBuzzzz (Exabytes Email Marketing) which is more suited to the needs regarding bulk email delivery.
3. Mailbox full
If the users experiencing the defer limit issue caused by a full mailbox, can login to cPanel -> Email Accounts, select the account that reaches the maximum email quota and then perform housekeeping to reduce email usage.
4. Email Forwarding
If a user experiences a defer limit issue caused by sending too many emails to the forwarding address, the user can log in to cPanel and delete the associated forwarding address.
Next please be advised that configuring email forwarder to free email service provider such as Hotmail.com, Gmail.com is strictly not allowed in shared hosting environment.