Images not showing in emails

Hello, I’ve followed the guide meticulously, ensuring all configurations for permissions, hotlinking, and more are properly set up. When sending emails via Roundcube from my domain to Gmail, images load seamlessly. However, when using the MailPoet application (both the service and custom SMTP), images fail to load. I’ve verified that the permissions on the uploads folder are correctly set to 755, as per the guide, and I’ve disabled hotlinking through cPanel. Additionally, I’ve conducted a test on mail-tester.com, receiving a score of 9.9, indicating no apparent issues.

Despite these efforts, I’m uncertain what else to investigate.