Error: Domain has exceeded the max defers and failures per hour

If you see this error in your mail server logs or email management panel, it means your domain has exceeded the maximum number of bounced or deferred emails allowed per hour.

• Why does this happen?

The system detects that too many emails were sent to invalid, non-existent, or temporarily unreachable addresses. To prevent damage to your domain’s reputation and protect it from possible blacklists, a temporary sending block is automatically triggered.

• Block duration

⏱️ The block lasts for 1 hour, after which the system will automatically retry sending the remaining emails, provided the error rate has normalized.

• Goal of the block: protect your domain reputation

Mass sending of emails to incorrect addresses is typical spammer behavior. If your domain starts behaving similarly, email providers (such as Gmail, Outlook, Yahoo, etc.) may flag it as suspicious and list it in public or private blacklists.

• Emails delivered to spam folders
• Emails completely rejected by recipients
• Loss of domain credibility