Mass Mail System Usage and Architecture used by ISP

[Deepak_5]

Hi ,

Has anyone worked on a mass mail system used by
Internet Service Providers for promotional schemes given by the customer.
If yes,
Here are the question.

1. Is there are site where I can find these
details.
a. Usage
b. Why should a guy go to these ISP's to
do this business. Why can't he send
them on his own, if he has the addresses.
2. How is it usally built ?

If anyone has any feedback, please let me know.

Thanks and Regards
Deepak