An Outlook user posed this question:
I'm trying to change the color of all of the messages which is coming from the local machine but no luck. Its working fine for other domains but not for the local domain.
The conditional formatting rule did not work because mail sent from Exchange mailboxes does not use the SMTP address (or have a message header).
You have two options: you can filter on part of the x.500 address which Exchange server uses for internal email or you can filter all mail containing an @, which will skip internal mail as the addresses do not contain an @.
A third option is to add a filter for all mail and create a second filter for mail containing an @. With this type of rule, you'll probably want to apply your filters only to read messages.
You can use a similar rule in Rules wizard. Look for @ as the word in an address and the rule will apply to all mail that originates outside of your Exchange sever. Use the method at Create rules that apply to an entire domain, with @ as the 'domain' name.
Conditional filter for Internal Email
Each Exchange mailbox has an x.500 address, which is in this format:
/o=Slipstick/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=alias
Using the organizational unit, or even just the /o= part in the conditional formatting will work for all mail sent using Exchange accounts. If you also want to apply the formatting to messages sent by services within your organization, such as from web servers, you'll need to include your domain name in the conditional formatting rule as well.
Conditional filter for All Mail
To create a filter for all external email, you need to put an @ in the From field of the filter dialog. Since mail sent by Exchange users does not have an @ sign in the email address, only mail sent from users outside of your Exchange server will be highlighted.