I'm trying to setup the autoresponder through Campaign Monitor, although b/c we're using Gravity Forms, the autoresponder won't trigger.
After speaking with their support team, they think Gravity Forms is using the bulk import API call, which is why it won't trigger.
Rather than the single subscriber API call addition here:
More on this topic from Campaign Monitor:
"Importing subscribers from a file does not trigger any autoresponders based on signup, nor does manually typing them into your account. Importing subscribers using the batch import API method will not trigger signup autoresponders either by default.
The batch import API method's default setting can be overridden by adding the QueueSubscriptionBasedAutoResponders parameter and setting it to true. Adding people via a public web form, or individually via the API will trigger the signup autoresponder as well."