Using Outlook 2010's Junk Filter with Multiple Accounts

If you use Outlook 2010, and run more than one account through it, the junk mail filter will have to learn what is junk and what is not for each individual account. This is not a Global Filter.

Slipstick - a great Outlook support resource site wrote something up about this.

Using Outlook 2010's Junk Filter with Multiple Accounts

...Outlook 2010's Junk Email filter options are individual, not global settings. Rather than applying one setting to all accounts, you can set different options for each email account in your profile. While its easier to change the settings when you deliver each account to a different data file, the settings are per account, not per data file, so you can change the settings.
When you use multiple accounts delivered to separate data files, the Junk Email options dialog shows the junk mail settings for the account whose folders you are in.

When more than one account is delivered to a data file, you'll need to open a message received by the account and click the Junk button to see the Junk Email Options.