My application needs to know if a user has opted out of the CC e-mail. Is there an API Event Handler that would allow a call back to the application? For example, how would my application "know" if the user unsubscribed? I suppose an alternative would be to iterate through all of the CC active contact to re-sync our application's database but that isn't ideal.
EDIT: I might have answered my own question: https://community.constantcontact.com/t5/Documentation/Frequently-Asked-Questions/ba-p/61737#Q2
Just in case this helps, we don't have a proactive webhook for this, but you could get an email that notifies you of this--you can set up notification emails that do this by logging into your account and going to Contacts>Sign-up Tools>Sign-up & Unsubscribe Updates.
You can get a list of people who unsusbcribed through the API by doing a GET to the contacts collection and specifying status=OPTOUT and modified_since=aDateYouPick as described on this page. Your application might make that call nightly to sync changes from our side.
I hope that helps!
Partner API Support Engineer