A retention tag is a rule that defines a retention period and an action. A retention period is specified as a number of days, or never, if you intend to allow items to be retained indefinitely. Actions include delete and allow recovery, permanently delete, and archive. The location of the archive is the user's archive mailbox; if they don't have one, nothing will happen here:
Retention tags
Retention tags can be Default (automatically applied to an entire mailbox), Personal (applied by users to specific files and folders), or automatically applied to a default folder:
Retention policies
A retention policy ...
