These instructions apply to Outlook 2011 versions 14.1 and 14.2, from Microsoft Office 2011 Service Packs 1 and 2. If you’re using the initial release of Office 2011, please see the Setting Up Outlook 14.0 section.
Go to Outlook’s Tools menu and select Junk E-mail Protection…. Turn off Outlook’s junk filter by clicking None and then OK.
Open Outlook’s Preferences window and click on Sync Services. Make sure that Contacts is checked and that it’s set to sync with On My Computer. This will let Outlook to sync its contacts with the Mac OS X address book so that SpamSieve can access your addresses and know from the start that your regular contacts aren’t spammers. (If the Sync Services list is empty, see this page or this page.)
Switch to SpamSieve by clicking on its icon in the Dock. Choose Install Outlook Scripts from the SpamSieve menu. After you quit and re-launch Outlook, you should see four SpamSieve items in Outlook’s Scripts menu:

Choose Rules… from Outlook’s Tools menu. Click on the source list item corresponding to the type of account you have (e.g. POP, IMAP, or Exchange) under “On My Computer”. If you have more than one kind of account, you will need to repeat the following steps for each account type.
If you had previously used SpamSieve with Microsoft Entourage, delete any SpamSieve rules that Outlook brought over from your Entourage setup.
Click the + button. Change the name of the rule to SpamSieve - Set Category.
For a POP account, under When a new message arrives it should say All Messages.
For an IMAP or Exchange account, it should say Folder Is INBOX (<Account Name>); you may have to choose Choose Folder… and type “in” to be able to select the inbox. Click the + button to add an additional condition for each IMAP account that you have. Click on If all conditions are met and change it to If any conditions are met.
Under Do the following, click on the - button to the right of Change status and Not Junk E-mail to delete the Change status action.

Click on the pop-up menu that says Set Category and select Run AppleScript.

Then click the Script… button and Select the SpamSieve - Set Category.scpt file. This file is stored in the Outlook Script Menu Items folder (which is probably inside the Microsoft User Data folder inside your Documents folder):

Make sure that Do not apply other rules… is unchecked. For a POP account, the rule should now look like this:

For an IMAP or Exchange account, the rule should now look like this:

Click OK to close the sheet.
Drag the SpamSieve - Set Category rule to the top of the list.
In the Rules window, as before, repeat the following steps for each type of account that you have.
Click the + button. Change the name of the rule to SpamSieve - Move Messages.
Under When a new message arrives, click on the pop-up menu and change it to say Category. Click on the pop-up menu for None and change it to Junk. The condition should now say Category Is Junk.
Click the + button to the right of Junk to make a new condition.

Click on From for the new condition and change it to say Category. Click on the pop-up menu for None and change it to Uncertain Junk. The condition should now say Category Is Uncertain Junk.
Click on If all conditions are met and change it to If any conditions are met.
Under Do the following, click on the - button to the right of Not Junk E-mail to delete the Change status action.

Click on the pop-up menu that says Set Category and select Move Message.

Change the menu at the right from None to Junk E-mail. The rule should now look like:

Click OK to close the sheet.
Drag the SpamSieve - Move Messages rule so that it is just below the SpamSieve - Set Category rule(s) (and above your other rules).
Now proceed to the Do an Initial Training section. To train SpamSieve with spam messages, select one or more of them and then choose SpamSieve - Train as Spam from Outlook’s Scripts menu. To train SpamSieve with good messages, select one or more of them and then choose SpamSieve - Train as Good from Outlook’s Scripts menu. The keyboard shortcuts for these commands are Command-Control-S and Command-Control-G.
SpamSieve will process new mail automatically. If you ever need to manually ask it to sift through a mix of spam and good messages, select the messages and choose Rules ‣ Apply All from the Message menu.
The above is all you need to know about using SpamSieve with Outlook. The Outlook Customization section explains some more advanced setup options.