Must be a new feature, but with a new server setup with InterWorx I saw the alternate SMTP 2 was not on by default. I clicked the install button to enable it and it worked great from my home computer.
I then started having clients call me that they could no longer send email. It eventually clicked that the new server must be blocking port 587 and checked the firewall. That was it!
I’m guessing you don’t add this by default because a user can select any port for the alternate SMTP 2, not just 587. So not sure if this is a bug or a feature request.
Maybe it would be possible to always update the firewall to allow connections on the SMTP 2 port. So on initial setup make it 587 and allow connection on 587. If they change it from 587 to 588, it would remove the allowed connection for 587 and add one for 588.