Are the Schedule automatic checks and Send email notifications options enabled in the Vulnerability Checker settings (wp-admin/admin.php?page=Extensions-Mainwp-Vulnerability-Checker-Extension)?
Vulnerability Checker emails are sent after a scheduled automatic-check cycle finishes. They are not triggered immediately when a vulnerability is detected during a manual check or site sync.
The email uses the recipient(s) configured for Daily Digest Email under MainWP Dashboard → Settings → Email Settings.
If no recipient has been saved there, it uses the WordPress Administration Email Address.
The Vulnerability Checker sends an email after the scheduled check cycle finishes, but only when at least one site has a detected, non-ignored vulnerability. It does not send an email when all results are clear.
You mentioned that some sites have alerts. Do those sites show a Last check date corresponding to the August 3 automatic check, and were the vulnerabilities still detected after that check?
Please also check the spam/quarantine folders for an email with the subject MainWP - Vulnerability check.
The notifications should have been sent out in that case.
Would you mind opening a private Help Desk ticket so we can collect some additional information & investigate further?
Please refer to this Community thread by its URL in the ticket.
WordPress® is a registered trademark of the WordPress Foundation, and WooCommerce® is a registered trademark of WooCommerce, Inc. MainWP is an independent product and is not affiliated, associated, or endorsed by the WordPress Foundation, WooCommerce, Inc., or Automattic Inc., except where noted under the Jetpack® API and Trademark License Agreement. All product names, logos, and brands are property of their respective owners and are used for identification purposes only.