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 forwarding address
Password: Your forwarding address password, or your application password if you have two-factor authorization enabled.
You can select to import your existing email folders and other information or you can create a new folder for imported information. This is up to you.
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: The name you would like your account to be called (Your first and last name).
Email address: Your forwarding address
User name: Your forwarding address
Password: Your forwarding address password, or your application password if you have two-factor authorization enabled.
Incoming (IMAP) server: Incoming server of your forwarding address
Incoming server port: 993
Authentication: Basic
Encryption: SSL
Outgoing (SMTP) server: smtp.pobox.com
Outgoing server port: 587
Check the box to "use different username and password to send email.
User name: You're Pobox email address
Password: Your Pobox password, or your application specific password
When you are done click "OK"
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.