You can turn off the server-side Junk Email Filtering for your mailbox.

OWA

  1. Log in to your Exchange mailbox via OWA.
  2. Navigate to Options and turn off automatic Junk Email filtering. Depending on your Exchange version,
    • OWA 2007: Navigate to Options > Junk Email. Select Do not filter junk email
    • OWA 2010: Navigate to Options > See all options > Block or Allow. Select Don't move email to my Junk E-Mail folder
    • OWA 2013: Navigate to Settings > Options > Block or Allow. Select Don't move email to my Junk E-Mail folder.
  3. Save changes.

Outlook

You can also disable the built-in Junk E-mail Filtering in Outlook:

  • Outlook 2010/2013:
  • Outlook 2007:

Now none of your messages will be moved to the Junk E-Mail folder automatically, i.e. all emails will be delivered to Inbox regardless of the Spam score.