How to re-authenticate inboxes:
Once the inbox has been re-authenticated, the red badge will disappear.
If you don't have access to the inbox:
If the inbox that needs to be re-authenticated is owned by another person (eg. a client inbox),
select the "Get shareable link to re-authenticate"
Copy the invite link and send it to the inbox owner. The inbox owner can then log in to their email account and re-authenticate the inbox.
An email will be sent to the admin (who created the re-authentication link) once the inbox has been successfully reauthenticated.