Backups Updated 2026-05-19

cPanel quota warning emails — getting them right

cPanel sends quota warning emails to end users. How to configure the threshold, customize the message, and avoid the failure mode where warnings go to nobody.

Quota enforcement without warnings produces angry support tickets. cPanel can send warning emails when an account crosses 80% and 95% thresholds. The defaults are sensible; the failure mode is that warnings go to the wrong address or to nobody at all.

What’s happening

cPanel’s quota warning system reads the account’s primary email address from /var/cpanel/users/<user> and sends warnings there at configured thresholds. The thresholds are set in WHM > Tweak Settings > Disk Quota Notifications. The warning emails come from the cPanel server itself; if outbound mail is misconfigured, they vanish.

The common misconfiguration: the primary email address is the same domain as the account being hosted, and that mailbox is on the same server. When the server is at quota and can’t deliver, the warning is the first thing that fails.

How to verify

Inspect the configuration:

whmapi1 get_tweaksetting key=quota_email_thresholds
grep -i contactemail /var/cpanel/users/<user>
exim -bp | head
tail -100 /var/log/exim_mainlog | grep -i quota

The user’s contact email is in /var/cpanel/users/<user> as CONTACTEMAIL. If it’s empty or unreachable, warnings fall on the floor.

The fix

  1. Set warning thresholds in WHM > Tweak Settings > Disk Quota Notifications. The defaults of 80% and 95% are reasonable; some teams add 90% for an intermediate trigger.
  2. For each cPanel account, verify the contact email is a mailbox not hosted on the same server. whmapi1 modify_account user=<user> contact_email=<external-address> for accounts hosted on their own domain.
  3. Customize the warning template if your branding requires it. WHM > Tweak Settings > Notification Templates. Don’t change the substance — the warning needs to clearly state usage, threshold, and the action the user must take.
  4. Test the warning path. Push an account temporarily over 80% (e.g., upload a large temp file), confirm the email arrives, then clean up. A warning system that has never produced an email is a hypothesis.
  5. Document the policy in the customer’s onboarding. The customer should know that warnings come at 80% and they’re expected to clean up before 95%.

Stack Harbor sets up and tests quota warnings as part of cPanel/WHM management onboarding.

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