Policy can be changed easily. Just create new policy and target that user group ou etc.

Retention is a little more tricky. You can change the retention that applied but only on the existing one that apllies. Say change from one to five years. Youcannot apply a new one.

Let me be a little more precise about the retention side of things as before I was in the middle of call of duty :-)

So if you have a user who has the retention category of business applied you can change the number of years from say one to five and this will apply to items retrospectively. You cannot however add a new one and apply this to existing items, only new archived items.

Since these employees no longer exist in Active Directory I cannot apply a policy and target an OU, just their archive exists

Is the end goal to prevent Storage Expiry from deleting the archives?  If yes, you can uncheck the box on the properties page of the Archives that allows them to be expired.

Is to actually allow expiry of these mailboxes and items within them, they originally assigned a policy and retention category which did not expire items.

If I cannot successfully change the retention category or policy on these archives does deleting the archive effectively and gracefully remove the items from the Evault Store?

Yes, deleting the archive will remove the items from the Store Partition, database entries, and indexes.

Regards,

Thanks