Hello Aditya,
Thank you for reaching out on the ThingWorx Developer Community.
Can you confirm which mail server you are attempting to utilize with this connector (Exchange, Gmail etc.)? Have you confirmed that there is proper connectivity between ThingWorx and this mail server?
We have an article which seems to cover generic issues when attempting to send messages with the Mail Extension. Please see here.
If you proceed through this article and are still having issues perhaps you could share a redacted version of the CBMSolutionsMailThing's Configuration page to ensure this is setup correctly.
Regards,
Tyler Misner
ThingWorx Technical Support Engineer