Why Your Domain's Email Sending Was Temporarily Blocked: "Max Defers and Failures Per Hour" Print

What the error means

If outgoing mail from your domain stopped working and you're seeing a bounce message similar to:

Domain yourdomain.tld has exceeded the max defers and failures per hour (25/25 (100%)) allowed. Message discarded.

this is not a hack notification and not a billing issue. It's a built-in mail server protection that kicked in automatically. It means too many of the emails your domain tried to send in the last hour either bounced outright (failed) or couldn't be delivered yet and were queued for retry (deferred). Once that ratio crosses the threshold we set on the server, the mail server stops accepting further outgoing mail from that domain for the rest of the hour, then resets.

This exists to protect you as much as it protects the server. A domain that keeps hammering dead addresses is the classic signature of either a compromised account sending spam, or a script/form with a bug, and letting that continue unchecked is what gets a server's IP blacklisted, which then breaks mail delivery for every domain on that server, not just yours.

The usual causes

In roughly descending order of how often we see them:

• A stale or dirty mailing list. Sending a newsletter or announcement to an old contact list that includes closed accounts, typos, or addresses that no longer exist.
• A compromised email account or WordPress site. Weak or reused passwords, or an outdated plugin, letting something outside your control send mail through your account.
• A misconfigured contact form or script. A "reply-to" or notification address that's wrong, or a form being hit by a bot submitting garbage email addresses.
• Sending to addresses on domains that no longer accept mail, or that have started greylisting/rejecting your server for unrelated reputation reasons.

How to check what actually happened

Log in to cPanel and go to Email > Track Delivery. Filter the results for "Deferred" or "Failed." That list shows you exactly which addresses bounced or stalled and why, which is normally enough to identify the source in a couple of minutes: one bad list, one broken form, or one obviously-not-you sending pattern.

How to fix it

1. If it's a mailing list problem: clean the list, remove bounced/invalid addresses, and consider sending in smaller batches rather than all at once.
2. If it's a compromised account: change the email account password and your cPanel password, check for unfamiliar auto-forwarders or filters under Email > Forwarders and Email Filters, and if it's a WordPress site, update all plugins/themes and scan for injected code.
3. If it's a script or form: check the destination address is correct and add basic validation or a CAPTCHA to stop bot submissions.
4. Once the cause is fixed, the block clears itself automatically at the top of the next hour. You don't need to wait for support to "unblock" you unless the underlying issue isn't resolved and it keeps re-triggering.

If you can't identify the cause from Track Delivery, or the block keeps recurring, open a support ticket and include the exact error message with the timestamp; that lets us pull the mail log for that specific window rather than guessing.

Preventing it going forward

• Keep any mailing list on a double opt-in basis and prune it periodically.
• Use a proper mailing list tool for anything beyond a handful of recipients rather than BCC'ing from a regular mailbox.
• Keep CMS plugins, themes, and core files updated.
• Use strong, unique passwords on every email account and your cPanel login.