Recently worked on case where disabled tag was applied to Inbox folder.
Emails in the Inbox when checked from Outlook in online are showing as the message is expired today.
Email in OWA shows ;
Thou these messages are showing as expired,they wont be deleted. These messages are showing as expired because the way the expiration date is calculated. Retention date is calculated based on values of 2 properties. It is the sum of the message delivery time and the retention period (ie Never), since the tag is disabled,the retention period is set to 0,thus showing as the message is expiring today itself.