Opt in email lists via asp

Can anyone here recommend some service for opt in email lists. My problem is that most services will take the user off the site to sign them up and the forms are very basic. I have some complex quote forms and contact forms where people can input alot of information. I'd like to be able to add people to this subscription list if they want after processing the detailed information that they have entered. But at the same time I want to keep users in categories based on the industries that they are in so we can send targeted emails based on their industry. Does anyone know of a such a services? I've looked into listserv and lyris list manager, but I won't be able to install these apps on the webserver. So they are pretty much useless. Does anyone have any experience with this? thanks.