To start, login to your Outlook account and click on the "cog" in the top right of your screen.
Next, click "Connected Accounts"
To add your Pobox account, click "Other email accounts"
Next input the following information:
Display name: The name you want your account to be called
Email address: Your Pobox address
Password: Your Pobox password, or your application specific password
Under Advanced Settings check the box to "Manually configure your account settings (POP, IMAP, or Send Only account)".
On the following page, select the account type you would like to set up and click "OK"
Next, please make sure you input the following information in the correct sections:
Display name: This is the name recipients of your messages will see (Your first and last name).
Email address: Your Pobox address
User name: Your Pobox address
Password: Your Pobox password, or your application specific password
Incoming (IMAP) server: mail.pobox.com
Incoming server port: 993
Authentication: Basic
Encryption: SSL
Outgoing (SMTP) server: smtp.pobox.com
Outgoing server port: 587
Click "OK" when complete
After you click "OK" you should see the following page confirming that your mail account has been setup correctly.
Click "OK" and you're ready to start using Outlook.com.