1. Login 2. Click on Email Security->SMTP 3. Click on Exceptions tab 4. Click on New exception list 5. Enter name "test" 6. Check Heuristic Anti-Spam checking 7. Check "For these source hosts/networks 8. Click on folder, drag Internal (network) 9. Click Save
Of course, it worked this time! I wonder why it didn't work the other time I tried it.