Most email blacklistings on shared hosting start with one compromised website sending thousands of messages an hour. WHM lets you cap how many messages each domain can relay and pause sending when too many bounce. Setting these limits protects every customer on your reseller plan.
Before you start
- WHM access on your reseller plan.
- An idea of normal sending volume for your customers. A small business mailbox rarely sends more than 100 messages an hour.
The two limits that matter
| Setting | What it does | Suggested value |
|---|---|---|
| Maximum Hourly Email by Domain Relayed | Messages per domain per hour. Extra messages are queued and retried, not lost. | 100–300 |
| Maximum percentage of failed or deferred messages a domain may send per hour | Stops sending for the hour when too many messages bounce, a sign of spam lists. | 50% |
Set limits in a package
- Go to WHM → Packages → Edit a Package.
- Select the package and click Edit.
- Set Maximum Hourly Email by Domain Relayed and Maximum percentage of failed or deferred messages.
- Click Save Changes. All accounts on the package get the new limits (see editing packages).
Set limits for one account
- Go to WHM → Account Functions → Modify an Account.
- Select the account and click Modify.
- Set the same two fields. You can enter a lower value for a suspected spammer, or a higher value for a customer with a legitimate need.
- Click Save.
Tip: Customers who send newsletters to thousands of people should use a dedicated email marketing service. Raising hourly limits on shared hosting for bulk mail puts the shared IP at risk.
Spot an account that is sending spam
- The customer reports messages "queued" or delayed: they have reached their hourly limit.
- In the customer's cPanel, Email → Track Delivery shows hundreds of messages to random addresses.
- Bounce messages arrive in the default mailbox in large numbers.
What to do if an account is compromised
- Lower the hourly limit to a small number or suspend the account while you investigate.
- Change the cPanel and email passwords (see changing a password).
- Scan the site with Imunify360 and remove malicious scripts (see cleaning infected files).
- Check contact forms and add CAPTCHA protection.
- Open a ticket so MdmHost can clear the mail queue if needed.
Troubleshooting
"Domain has exceeded the max emails per hour allowed"
This bounce or log message means the limit worked. Messages are retried automatically in the next hour.
The field cannot be set above a certain number
The server administrator sets a maximum for resellers. Contact support if a customer has a genuine need.
Frequently asked questions
Do limits apply to incoming email?
No. They only count messages sent or relayed by the domain. Incoming mail is not limited.
Do forwarders count toward the limit?
Yes. Forwarded mail is relayed by the server, so a forwarder receiving spam can use up the hourly limit. Prefer mailbox delivery over forwarding to free mail providers.
Is 0 unlimited?
Yes, 0 means no per-domain limit, which then falls back to the server-wide default. Always set a number for reseller packages.