This tutorial will let you send emails from an @a1steam.com or @p2steam.com address via Outlook.com. Your incoming mail will still be forwarded to your Outlook.com/Hotmail inbox.
In Outlook.com, click the Preferences cog and then click the “Options” menu item
Click “Your email accounts”
Click “Add a send-only account”
Enter the name as you want it to appear to recipients, and the account details I emailed you
Hopefully there is no Step 5! The A1 server has auto-configure enabled so if the account details are correct, it should have just worked. You should now be able to send email from your new account.