Is it possible to check if a user has read an email in O365 and when through the admin portal. I am being asked by senior management. The sender hadn't set a received or read receipt flag when sending.
As Vasil mentions, you would need some EWS scripting or something like Search-Mailbox cmdlets with the -LogLevel switch which isn't straightforward. You could possibly assign full mailbox access to the mailbox and go in and see through Web Access if the message has been read - however this raises issues in itself so I wouldn't recommend it.