SOLVED: How to Setup Office 365 Email on a Windows Phone 7 Mobile – Cell Phone

The key thing you need is to set your WP7 phone to use is the server m.outlook.com.  Below is the full explaination from Microsoft:

If this is the first e-mail account you’ve set up on the phone, tap the E-mailtile on the phone’s home screen and skip to step 4. If this is not the first e-mail account you’ve set up on the phone, swipe left from the home screen.

1. Tap Settings and then tap E-mail and Accounts.
2. Tap Add an Account and select Outlook.
3. Enter your e-mail address and password and tap Sign In. Windows Phone will try to configure your e-mail account automatically. If configuration completes successfully, skip to step 7.
4. If your e-mail account can’t be configured automatically, tap Advanced Setup. You’ll need to enter the following information:
• E-mail address  This is your full e-mail access, for example tony@contoso.com.
• Password   This is the password for your e-mail account.
• User name   This is your full e-mail address, for example tony@contoso.com.
• Domain   This is the part of your e-mail address after the @ sign, for example contoso.com.
• Server   For instructions for finding your server name, see the Finding the Server Name section below.
• Select the Server requires encrypted (SSL) connection box.
5. Tap Sign In.
6. Press OK when Exchange ActiveSync asks you if you want to enforce policies on your phone. Policies let you set a password on your mobile phone and use a remote device wipe to clear all data from your mobile phone in case the phone is lost or stolen.

From: http://help.outlook.com/en-us/140/dd936215.aspxv