capturing emails

Does anyone link their website's "subscribe to our emails" button to Altru instead of direct to Constant Contact (or equivalent)? When our constituents sign up for emails, that think they are giving us their information, when in actuality their name, email, and zip code have gone to Constant Contact, and we may have no sign of them.

If you have figured this out, how do you set it up on Altru? What does it link to?

I appreciate any thoughts.

mayada