Ninad:
hello? you send a 500kb attachment to a mailing list? assuming there are 200 people on this list, that's a bandwidth of 100MB wasted!! Do you like wasting resources this way? If you ever post to a mailing list, you post URLs to a uploaded file, or send it directly to person involved. Even a attachment of more than ~10kb is generally frowned upon in mailing lists.
I sincerely hope you brush up on your netiquette.
- Ashish.