Dynamic distribution list -RecipientFilter not working

Question

I use the recipientFilter for DynamicDistributionGroup. Like this:
PS> set-DynamicDistributionGroup -identity UserPolicy -RecipientFilter "{((Department -eq 'ourDepart'))}"

And i can check this using as below command:
PS> Get-Recipient -RecipientPreviewFilter (Get-DynamicDistributionGroup "userpolicy").RecipientFilter

It can show the correct result from output:
Name RecipientType
---- -------------
Alvin UserMailbox
Alvin XXX Test UserMailbox

But why i didn't get any mail after i use the userpolicy@xxxxxxxxxxxxx .com for recipient?

My Enviroment is Exchange Server 2019 on Windows Server 2019.