It is currently not possible to change an existing user's email address. This applies to email/password user, SSO user, and Github user types.
Invite the new email and create a new user.
Invite the new SSO user with the new email and create a new user.
If needed, the old SSO user can be deleted by the HCP account owner.
Github Primary Email
When a user signs up for HCP using their GitHub account, HCP associates the user’s primary GitHub email with their HCP account. Even if the user then changes their GitHub primary email, HCP still will report the old primary email account. This is currently expected behavior.
There is a possible workaround for this scenario. Hashicorp recommends that the user will need to sign up with HCP again using email/password or invite a new user with the correct email to the current organization. Please open a support ticket for additional assistance.
Ownership Change (Optional)
If an ownership change is needed in order to make the new email/password or Github user the owner, please follow the steps listed in How-to Request HCP Ownership Changes.
NOTE: SSO users cannot be made owners of HCP accounts. The owner user must be an email/password type user or a Github user type.