set managed folder mailbox policy on server mailboxes

The pshell command below will apply deleted items retention policy on all the mailboxes homed on a server. Please note that this policy is set on exchange organization level
 Get-Mailbox -Server "servername" -ResultSize unlimited | Set-Mailbox -ManagedFolderMailboxPolicy "Deleted Items Retention Policy" -ManagedFolderMailboxPolicyAllowed
use this pshell command to manually start the MRM service
Start-ManagedFolderAssistant -identity "servername" 
To set the schedule for the managed folder policy to run,
1. From exchange mgmt console, go to server configuration, click on mailbox, right click on your server, and click on properties
2. Click on messaging records management tab
3. Click on customize and choose desired schedule