I want all e-mails that come from outside my organization to be highlighted in one color. Is this possible?
Yes, it’s possible, and there are two ways to do it.
If you use Exchange server, create an automatic formatting rule in a view to apply the color. The only criteria is the @ symbol in the From field on the Filter’s General tab. This works because messages sent from other Exchange server users don’t have an @ in the sender’s address.
If you don’t use Exchange it’s trickier to set up but still possible with two automatic formatting rules. The views filter does not offer exceptions, so you need a rule that applies a color to messages From @yourdomain.com and a second rule that applies a color to every message (don’t set up a condition).
The rules are applied in the order listed, with the formatting set by the first rule that applies to the message.
This method also works with Search folder and filters on Views. If you want to filter messages using Rules and Alerts, create a rule that looks for messages from a person or distribution list. Enter @ in the address field and when Outlook asks you to resolve the name, click Cancel on the Check Names dialog.
This tip comes from from a Slipstick Newsletter.
Another way of highlighting e-mails is to create conditional formatting rules. Go to the View tab >View Settings >Conditional Formatting.
Add a new rule, “From Outside” and set font and/or color. Then click Conditions. Under the Advanced tab, set a new field with From not containing your own domain.