If you are having issues with sluggish Outlook with a Microsoft Exchange account, try enabling Cached Exchange Mode.

If you want to control disk space utilization on RDS servers, you probably want to disable Cached Exchange Mode.

Disable Cached Exchange Mode on a RDSH by adding a registry key.

For Outlook 2010:

HKEY_LOCAL_MACHINE/SOFTWARE/Policies/Microsoft/Office/14.0/Outlook/OST

In that key create a DWORD named NoOST and set the value to 2.

Here's how to configure Outlook for Cached Exchange Mode.

In Outlook:

File → Account Settings → Account Settings (drop list)

Then:

Email (tab) → select Exchange account → Change (button)

Further:

Exchange Server Settings (window) → select Use Cached Exchange Mode (checkbox) → Next

You should be back at the Email Accounts window. Click Finish.

You should see a notification window that advises you to restart Outlook in order for the change to take effect.

When you re-launch Outlook, it will begin to make a copy of your Mailbox contents onto your local computer. This will take some time. Not all items will be immediately available. If you have a large mailbox or a slow Internet connection, this can take an hour or more.

In Outlook, go to:

Tools → Account Settings → Email (tab) → Microsoft Exchange Server → Change

Then:

Exchange Server Settings (window) → select Use Cached Exchange Mode (checkbox) → Next

You should be back at the Email Accounts window. Click Finish.

You should see a notification window that advises you to restart Outlook in order for the change to take effect.

When you re-launch Outlook, it will begin to make a copy of your Mailbox contents onto your local computer. This will take some time. Not all items will be immediately available. If you have a large mailbox or a slow Internet connection, this can take an hour or more.