There's a new version of the HubSpot API

As of November 30, 2022, HubSpot API Keys are being deprecated and are no longer supported. Continued use of HubSpot API Keys is a security risk to your account and data. Your API Keys could be deactivated at any time after Nov. 30th, and we recommend that you migrate to Private Apps as soon as possible so you do not lose business-critical functionality.

How Does HubSpot validate email addresses?

HubSpot will validate the email address used for any process that would create or update a contact record.  This includes using the Contacts API to create or update a contact directly, and also the processing of any form submissions or events. Learn more about how HubSpot validates email addresses.