Using the API we are trying to see which CTAs are open for a given user’s email account. We send a query and get a response that the result is false, and the is an Unknown data type of the field - EMAIL. Username fails as well though full name does work (which is our workaround). 

Per L2 Support “After re-visiting this behavior with our product and architect team, this is treated as an expected behavior as per the product setup as the "Email" datatype field isn’t supported in the filter section of Cockpit/CTA and SuccessPlan APIs.
 
The Engineering team considered this as an enhancement and started working on this development. Our team is requesting you to please log an idea community post as a track for this enhancement from your side. The Product team will soon get back to you on the post-logged with an update.
 
And for the time being, we request you to go with the workaround suggested i.e., using the full name field in the filter section.