How to allow users to bypass CSF's SMTP_BLOCK

Warning: Way to the Web Ltd. (the company behind ConfigServer) closed permanently on August 31, 2025, and has released CSF under the GNU General Public License v3.

cPanel now publishes and maintains a public fork of CSF focused on critical security and stability fixes.​

For more details, see:

ConfigServer Services Announcement

Question

How do you allow users to bypass CSF's SMTP_BLOCK?

Answer

1. Log in to WHM as the root user.
2. Navigate to Home / Plugins / ConfigServer Security & Firewall.
3. Click the csf tab.
4. Click the Firewall Configuration button.
5. Select SMTP Settings from the dropdown menu.
6. Scroll down to the SMTP_ALLOWUSER setting.

7. Add the cPanel user's username in the SMTP_ALLOWUSER textbox.

   Note: usernames must be separated by a comma.

8. Click the Change button at the bottom of the page.
9. Click the Restart csf+lfd button.