At times, an account on shared hosting or reseller hosting plans may temporarily be limited from sending new mails. This commonly occurs if the domain exceeds the max defers and failures per hour. 

We will discuss the meaning and causes of "max defers and failures per hour" errors.

What is "Max Defers and Failures Per Hour" Error?

If you are receiving an error similar to "Domain example.com has exceeded the max defers and failures per hour (5/5 (100%)) allowed" in an email bounce message, it means that your domain has triggered a rule in the server that will temporarily prevent any email being sent from the account. This happens when a domain account sends out emails that either fail or get deferred by the recipients mail server.

Failures can result from a variety of issues, including:

• misconfigured email headers
• too many connections to the email server from your IP address
• multiple emails flagged by spam filter
• spam complaints received
• improperly configured email relay
• Inconsistent SPF/DKIM records
• Other errors

If the combined value of failures and defers within an hour exceed the Hosting Plan's preconfigured limit, SMTP access will be restricted. This prevents the account from sending further mails until the limit is reset.

Prevent "Max Defers and Failures Per Hour" Issues

This error is derived from an hourly monitoring system, where any blocked domains are allowed to send email again after the server's hourly cron job runs. 

Note: Mail statistics are collected by cron jobs that run every 5 minutes or less.

To avoid Alternatively, you can upgrade your hosting plan to receive greater email resources.

Read also: Understanding Email Defers & Failures Limits