Hmmm, maybe you didn't actually start out on the same page as Pantera (some misunderstanding like you mean the Nokia Messaging SERVICE, while others are talking about the SOFTWARE - which isn't available for the N900 - or similar).

One easy solution for you, (if you're new to Nokia anyway, and haven't yet given your Nokia address to everyone) may be to just use a different address - from a provider that is in your list with country set to India.
Another one: always check your e-mail (Nokia or other) online with the browser. I do that with gmail, it's really not that bad, with browsers like MicroB, Firefox, Opera Mobile and Chrome to choose from....

If you're absolutely set on using the nokia e-mail address AND the default e-mail client on N900, try doing a walkthrough of the setup process with screenshots showing every single step, like e.g. here:

http://www.nokian900.tv/configuring-...k-in-the-park/

or here:
http://thenokiablog.com/2009/10/19/n...-review-email/

or here:
http://zomgitscj.com/2010/03/07/intr...he-nokia-n900/

It would be pretty strange for nokia messaging service not to be available in india, especially if you were able to register for it without any problems...