In order to use ActiveSync make sure this service is enable for your account. Click here for instructions on how to enable ActiveSync service.
From the Start screen, flick the screen to the left to access the App List. Pan through the App List until you locate the Settings option, and then tap it. Next, tap the Email & Accounts option, followed by the Add an Account option.
1. Tap the Outlook option.
2. Enter your e-mail address and password then click the Sign In button.
If your server can be located, Windows Phone 7 will use the server's Auto Discover service to automatically provision the phone to access your Exchange mailbox. Choose advanced setup is this is not the case.
3. Select Advanced setup and choose Exchange Active-sync.
4. Enter the following details:
-username: full email address
-password: mailbox password
-Domain: leave this empty
-Server (Exchange 2010): email.hostaccount.com
-Server (Exchange 2013): email.h01.hostedmail.net
Click Sign in
5. Select the data you want to download and specify how long you want to store messages on your phone.