You cannot have a different retention policy for primary and archive mailbox. The policy applied to the primary mailbox also applies to the archive mailbox. There are two most common scenarios where policy which is applied to the primary mailbox applies to archive mailbox are.
1) DPT with action other than move to archive action.
2) Archive mailbox having the same folder name ,which is already been tagged in the primary mailbox.
DPT with action other than move to archive action.
DPT with action other than move to archive action processes the primary mailbox as well as archive mailbox.
Emails deleted from archive mailbox are moved to the dumpster of archive mailbox.
Archive mailbox having the same folder name,which is already tagged in primary mailbox.
Lets consider below example, Policy applied to user CWade’s mailbox has one tag for Inbox with retention period of 365 days. Emails in the Inbox of primary will be tagged by the Inbox tag.
User creates a folder called "Inbox" in the archive mailbox and moves some emails to this folder.
RPT applied to the Inbox of the primary also applies to Inbox of archive.Emails older than 365 days are also deleted from Inbox of archive.
Above example shows that Inbox folder of archive mailbox is processed by the same tag which is applied to Inbox of Primary mailbox,since the folder names are same. This also applies if we have applied Personal tag to a folder in primary mailbox as folder with same name exists in archive.
This is by design,Applying a disabled Personal tag to Inbox of archive would not help,it would be overwritten by RPT applied to primary inbox.if don’t want Inbox in the archive to be processed,change the name of Inbox folder in archive.