Overview
The “MailboxNotEnabledForRESTAPI” error occurs when a mailbox isn’t enabled to use the REST API (used by applications to access mail, send emails, and other services in Exchange Online or Office 365). This can happen for several reasons, often relating to the type of mailbox or its settings.
Causes
This error often occurs when using the Microsoft 365 / Outlook.com mailer in an SMTP plugin like WP Mail SMTP. It indicates that the email account you’re using doesn’t have REST API privilege, which can happen due to the following:
- The mailbox is inactive or not provisioned
- Mailbox type not supported by API
Solution
To resolve this error, you’ll first need to ensure REST API is enabled for your mailbox account.
If you’re in a hybrid Exchange environment (where some mailboxes are on-premises and some are in the cloud), the error might occur because the on-premises mailboxes don’t support REST API calls.
You’ll need to migrate the mailbox to Exchange Online or configure your environment to ensure the API can access the mailbox. For steps on how to migrate your mailbox account, please see Microsoft’s official documentation.
Note: If your mailbox account doesn’t have admin privilege, you’ll need to contact your organization’s Global admin to migrate your account.
That’s it! Now you know how to troubleshoot and resolve the ‘MailboxNotEnabledForRESTAPI’ error.
Want to explore available email service providers WP Mail SMTP supports? Be sure to check out our complete guide to WP Mail SMTP mailers.