In your documentation you talk about how you would check to see if an email address exist or to get information for a contact, but what you didnt explain is how exactly would one query such thing.
Hello,
The best way to query if the email already exists or not is to run a search for this email address. The best way to do that is listed here. If it is listed, it will send you a response with the contacts information in XML format. If it is not listed it will send a response with no results.
If you have any questions please let me know.
Regards,