The domain custom.mbmail1.com is hosted on an AWS EC2 server. Since it’s not routed through Cloudflare, its IP directly connects to an AWS server. This server has only two ports accessible: port 22 for SSH and port 80 for HTTP. Notably, it lacks port 443, which is essential for HTTPS connections. Consequently, the domain is unable to support the HTTPS protocol. This is a common reason why HTTPS protocol may not work for an Action URL hosted on such a server.
If you still want the HTTPS protocol for your Action URL, please contact MailBluster Support and share the preferred Action URL (e.g., action.yourdomain.com) you want to set up in your brand. We’ll provide the necessary DNS records, which you’ll need to add to your domain’s DNS record list