If you want Outlook to never treat the email from people you send to as junk mail, have Outlook automatically add them to the Safe Senders List. To do this:
1. Click Actions, mouseoverJunk E-mail, and select Junk e-mail Options.
2. Select the Safe Senders tab.
3. At the bottom, check the Automatically add people I e-mail to the Safe Senders List checkbox.
4. Click OK.