Hi Soniya,

I trust that you are well.

Here is a sample that addresses your need :)

http://dev.office.com/code-samples-detail/1712

This sample shows how to build an MVC web application that uses Azure AD for sign-in using the OpenID Connect protocol, and then calls a Office 365 API under the signed-in user's identity using tokens obtained via OAuth 2.0. This sample uses the OpenID Connect ASP.Net OWIN middleware and ADAL .Net.

You can then re-use some of the code snippets from the above solution links that I posted to call the O365 Api for sending mail.

Please mark this thread as answered if it helps you.

Regards and Best of luck.

Brent