How to test SMTP email sending capability, locally?

Solution 1:

The only way you can test all the possible combinations is to set up or connect to servers that use them all. There is simply no other way. If you're going to test this on your workstation then don't set it up under Windows 7. Install Virtualbox (or whatever other virtualisation system you like) and install virtual machines that have the various configurations you want to test against.

Solution 2:

hMailServer open source e-mail server for Windows is great for this.

The mail handler itself is a Windows service. The admin control panel is a GUI Windows app. You can run any combination of configs at the same time (mail protocol, port, authentication, encryption, forwarding, etc). After changing a setting in the admin program, it will stop and re-start the service for you, instantly.

Installing on the same machine is okay. Installing on another machine in your network is better. Ideally the server should be on a different IP address than the client, but it works fine on the same IP address.