simplest solution for .net service to send mail securly?
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whats the simplest method for creating a web service to send emails?

I have a web app (static html pages) I want to upgrade to using web service of some sort along with some UI technology to communicate with the pages to the services.

I want to know what are my options for the web service part itself as well as what UI technology to use to connect to the services?


some typical things i need to accomplish is:
1. saving email addresses from the newsletter signup (text box and button)
2. sending an email generated by the contact us form and storing to the DB (text boxes and button)
3. log in for clients (username password authentication)
4. multiple data related tasks such as add data from UI and present data on the UI from the DB

I was thinking to try rest for the email sending, but don't know enough to decide just yet to start development... 

I'm not sure if i should use AJAX, JQUERY, JSON, SOAP... for getting the UI wired up to the web services.

What are my options for the web service part itself as well as what UI technology to use to connect to the services?
