I have a odd instance where by an email (password reset) from one of our third-party providers is being redirected to a shared inbox rather than the user it was intended for.
I can see on the original email it is set To: <> however the email never appears in that users' inbox, it goes straight to the shared inbox. This is confirmed by performing a Mail Flow trace on the email, whereby the email doesn't exist when searching for emails sent to the user, rather it appears on emails sent to the shared inbox.
I have checked the headers of the email and can see no transport rules have been triggered.
This only happens maybe once a week, whereby during this week, plenty other users receive their password reset email just fine.
The third party whose emails these are, have confirmed from their end the email was sent to the user and their Mail Flow shows the email as being delivered to the intended user account.
Any advice or pointers as to how I figure this one out would be gratefully appreciated.