We're looking for a way to simulate a user submitting the "Join My Mailing List" form via the API (or simple HTTP GET or POST). The main reason we want to do this is that we have a sign-up process established into our websites already and we don't want to give that up. We want the new subscribers to have the "Awaiting Confirmation" status instead of the "Active" status like we currently get from the API.
The 'Awaiting Confirmation' status can be achieved through the API as well as the Join My Mailing List form provided in the UI. This is an effect of turning the on the "Confirmed Opt-In" option on in your account. You can do this by clicking on the "My Settings" tab, followed by the "Confirmed Opt-In" link on the right hand side. You can find more information about Confirmed Opt-In in this FAQ.
Another thing worth noting is that if you have Confirmed Opt-In turned to "ON", in order for contacts to be set to the "Awaiting Confirmation" status they would need to be added using the "ACTION_BY_CONTACT" Opt-In Source. Using "ACTION_BY_CUSTOMER" would set them to active and bypass the "Awaiting Confirmation" status altogether.
I hope this helps. Please let us know if you have any other questions or concerns regarding this.