Hi Mahesh, have you already tried the ThingWorx Tutorial on this? It's covered quite extensively. Additionally there's also a Mail Extension available which you might want to have a look at.
Hope this helps.
There is a known issue with the Mail Server Extension and VPNs. Please review this KCS article and let me know if you have further questions on this: https://support.ptc.com/appserver/cs/view/solution.jsp?n=CS236135
I tried with exploring following,
1. Check for port
tried with suggested command and getting below error,
Connecting To SMTP.gmail.com...Could not open connection to the host, on port 25: Connect failed
Tried with below port also but result is same with port number changed.