If you want to “update or create” contacts, consider using the Update a
contact endpoint instead.
Request
Body
The contact’s email address.
The contact’s first name.
The contact’s last name.
You can use groups to segment users when sending emails. Currently, a contact
can only be in one user group. Read more
Manage mailing list subscriptions.
Include key-value pairs of mailing list IDs and a
Include key-value pairs of mailing list IDs and a
boolean denoting if the contact
should be added (true) or removed (false) from the list. Read
moreCustom properties
You can also include custom contact properties in your request body. These should be added as top-level attributes in the request. Custom properties can be of typestring, number, boolean or date (see allowed date formats).
There are a few reserved names that you
cannot use for custom properties.
To empty or reset the value of a contact property, send a
null value.Response
Success
The ID of the new contact.
Error
If a matching contact already exists in your audience, a409 Conflict error will be returned. All other errors will be 400 Bad Request.
An error message describing the problem with the request.

