Hi Jeff,
Based on my research, the Junk Email Filter options are on a per-account basis. If you want to manage junk emails for a shared mailbox, you need to use Outlook Web Access:
1. Log into OWA using your mailboxs credential.
2. Click your name in the upper right, then select
Open another mailbox in the list.
3. Type the name of the shared mailbox in the pop up window and click
open to enter the shared mailbox in OWA.
4. In the OWA of the shared mailbox, click the settings icon in the upper right, then select
Options to enter the OWA settings page.
5. In the
block or allow tab of the options page, you can then configure the safe senders or blocked senders in the list.
If I've misunderstood something, please feel free to let me know.
Regards,
Steve Fan
TechNet Community Support