I have configured exchange Microsoft exchange for sending mail from soar. I used to get the mail but all on a sudden it stopped. Getting no error. 
Can any one guide me how to solve this? Or any troubleshooting method is also fine for me. 

Hi there,

Review https://www.ibm.com/support/pages/node/7145826 where it describes how to enable debug in the app.config of the application.

Once you have enabled debug and reproduced you can download the logs (https://www.ibm.com/docs/en/sqsp/51.0.0?topic=apps-app-host-logs#reference_btj_ygy_vmb__title__2) and review them to see what is happening at the time it sends the email. Look out for SMTP error codes returned. If you get any of them search on line or work with your SMTP administrator.

If you suspect it to be a problem with the Outbound Email code you can open a case with IBM Support (https://www.ibm.com/support/pages/how-open-case).

Thanks BEN,
I am going for opening a support case.