I have a custom SMTP server that I need to deploy to Azure and call from outside of Azure.

This is a .Net worker service.

I've tried to deploy it as a webJob running in an App Service but I can't listen on the SMTP port (587). I don't think it's possible to open a socket from within an appService/webJob. Is it?

I could do it with a VM, but I am trying to avoid that if possible.

How can I open a socket in a webJob, and receive traffic from outside of Azure?

If I can't, what is another option for running the worker service?