The HTC Desire and Legend units feature an updated HTC Exchange ActiveSync client, offering the same push-based bi-directional synchronisation offered by the Hero and the Tattoo, but now also offering the ability to set and edit Out of Office status and message as well as supporting remote device wipe from Exchange as well as the ability to enforce password usage via ActiveSync mailbox Policy.

Setting up the Exchange email account is very similar as on the Hero and Tattoo models.
Launching the mail client for the first time will prompt you to select the type of email account you want to configure:

Select Exchange ActiveSync:

Select the option for Manual Setup:

Enter your full email address.
In the Server Address field enter the external name or IP address of the Exchange server (depending on how the administrator has configured the Exchange server - contact your IT department for the correct settings to use). This is usually the same address used to access Outlook Web Access webmail, in the form "exchange.mycompany.com"
In the Domain field enter in the domain which your user account is in - again contact your IT department for the correct settings to use. Usually, if you have a Windows PC in the office, this will be the contents of the "Log Into" field you use to access your PC (the third field below both "username" and "password" when logging in).
Enter your username and password - these will be the same details you use to log into your Windows PC.
Tick the option to use SSL if required by your Exchange server. If you don't know whether your Exchange server does or not, a handy way of telling is checking the address used to access webmail - if it begins with "https" then it does use SSL. If it just uses "http" (and doesn't redirect to an https address) then there is no need to use SSL.

Tap Next. If your Exchange server uses a self-signed Exchange certificate, you may be warned that the identity of the certificate cannot be verified, select the option to Continue:

Select which mailbox data you want to synchronise:

If your Exchange server has enforced security policies requiring password usage, you may be prompted to accept this requirement. Click OK:

Your mailbox data will now be synchronised. This may take a few moments depending on how much data is in your mailbox and which options you selected to sync.

Within the menu you can access Out of Office settings:

The Settings menu allows you to define how far back into the past you synchronise as well as how often mail is delivered:

NOTE - the default selection is for mail to be delivered every 15 minutes, so to enable true push you will need to adjust this option to "As items arrive":

Once synchronised, the device will be listed in the Mobile Options view within Outlook Web Access:

From here a remote wipe operation can be instigated in the event that the device has been lost or stolen, or you simply want to hard reset the device. Once complete, you will receive notification in your Exchange Inbox:

Once the Exchange account has been configured, you will be able to search the Exchange Global Address List (GAL) directly from the device:

You may also want to enable the LED notification light for new email messages: