Magento 2 SMTP Email Extension manages email queue retries by storing failed emails in a queue table. When an email fails, the system marks it for retry instead of dropping it. Retry attempts run on scheduled cron jobs. These jobs resend emails after a fixed gap. Magento 2 SMTP Email Extension also logs error reasons like timeout or auth failure. Admins can review logs and fix settings. Once corrected, queued emails are sent again. This process improves delivery, reduces loss, and keeps order, invoice, and notification emails moving without manual resending effortlessly.