You can download Freeware ArGoSoft from download.com 

https://download.cnet.com/ArGoSoft-Mail-Server-Freeware/3000-2369_4-10038331.html

or from our site here

  My Windows IP is : 192.168.2.171

  My Windows Gateway : 192.168.2.1

• Click Options to setup 

• Stop and Restart

Sample to test it on cpu_alert program 

It is free and simple, may or may not work for you but public SMTP Hotmail/Yahoo/Gmail is not working