Don't remember email address used to activate Microsoft Office

I think poor Girish has been beaten up enough.  If you carefully read his post and follow the link, http://commerce.microsoft.com/help , it does indeed take you to a very helpful site to resolve your issue, at least in 2016.

What you need to know:

1. If you don't have an MS account created, create one.
2. Save this account information (user name and password) so you don't have to go through this misery again.
3. The email address you use doesn't have to be a Microsoft email address, feel free to use your standard address.
4. If it was a retail purchase, know where you bought it and from what country.

What I found;

1. Once on the help site
2. Click on Manage Subscription
3. Click on Manage My Microsoft Subscriptions
4. Click on Contact Support
5. On the Contact page, click Get Started
6. Restate your problem, you'll get a bunch of stuff that's not useful.  In the chat box, scroll down and click on Talk to Someone.
7. Surprisingly, you'll not have to restate your issue, just confirm that their understand is correct and proceed with the chat.

Just be prepared to answer what they ask and you should be good to go.

Worked for me,

Good luck