Calling all developers

Hey Guys,

Now i was wondering if anyone could help me at here.

I am looking at starting a service that will allow users to be able to opt into differant categories of there own choice. And collect there information in a database.

What I would like to be able to do is this.

I would like someone to be able to use the service to be able to put a message together and then email that message to a particular category.

For example, I have 10 differant category's ranging from fishing, food, business etc etc.

Someone wants to send a message to everyone on the fishing list.

I would like them to be able to do this straight off the website without having to invovle anyone else.

Would this be hard to organise? I would be charging for this service so I would like the user only to be able to send there message only after they have paid.

I have been looking at autoresponder services, but what I want is an automated system where people can opt in, and other users can send messages to the users on the lists.

Any advice would be appreaciated. I am in the process of building the front end ( after about 6 weeks of layout changes ) and look to be finished in the next 6-8 weeks. BUt would like to add the back end functionality to it.

Cheers,

Timbor