Note that the email address must be properly URL encoded, as shown
above with '@' sign being translated into %40. The period does not need
to be encoded.
If a contact with that email exists, the query will return the
contact's <entry>, the same way it would be returned when you
query the contacts collection. In order to get the contact details, you
need to query the contact resource itself. If no Contact with that email address exists, the API will return
either a 500 error (Server Error) code or will return an empty feed
(i.e. a feed with no entries).
You can find multiple contacts with a single query by simply adding additional parameters:
Just like before, the returned feed will contain entries for any
Contacts that are found. Any that don't exist will simply be skipped.
Since all email addresses in Constant Contact are stored in
lowercase, please lowercase the email address you use for your query
parameter. If not, your case will not match and your query will not