>    first of all, thank you for having implemented 
the .MHT 
> file creation.
>    I need some pointer to the documentation available for 
> this format.

"MHT" format is in fact a regular RFC-MIME message (I 
wouldn't have implemented a proprietary format), which is 
described in RFC 2045 to RFC 2049:
<http://www.ietf.org/rfc/rfc2045.txt?number=2045>
<http://www.ietf.org/rfc/rfc2046.txt?number=2046>
<http://www.ietf.org/rfc/rfc2047.txt?number=2047>
<http://www.ietf.org/rfc/rfc2049.txt?number=2049>

And of course RFC 2822 for general information about 
Internet Message format:
<http://www.ietf.org/rfc/rfc2822.txt?number=2822>