The ‘redirect_uri_mismatch’ error originates from Google and occurs during the setup process. It happens when there’s a discrepancy between the ‘Authorized redirect URI’ in your Google web app and the one provided in your SMTP plugin’s settings.
We’ll show you how to fix this using WP Mail SMTP as an example.
Resolving the Error – Solution
To correct the ‘redirect_uri_mismatch’ error, log into your Google Cloud Console, locate your web app, and set the ‘Authorized redirect URI’ to ‘https://connect.wpmailsmtp.com/google/‘.
If you continue to face this issue, you may want to retrace the steps to set up the Gmail SMTP using WP Mail SMTP’s tutorial on Google Workspace / Gmail mailer.