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Highlight the folder you want to set the retention policy to:
Click Assign Policy in the toolbar (you may only see the icon), then Set Folder Policy.
Note: Do not click a retention policy directly from that drop-down; it will apply only to the email visible, not to the entire folder.
Click the Folder Policy dropdown and select the needed policy, then click OK.
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Right-click the folder you wish to change the retention policy for.
Hover over Assign policy.
Select the needed policy.
