Is it possible to disable outlook users from connecting to Exchange 2007 not using Cached Mode?
Absolutely. You can use the Exchange Management Shell cmdlet Set-CASMailbox to set multiple client access attributes for POP,MAPI,IMAP,EAS, and Outlook Web Access, and one of them allows you to specify whether Outlook can be used in online mode or only in cached mode. The parameter, of type boolean, is called MAPIBlockOutlookNonCachedMode, and gets a default value of False.
In order to disable a user (for example Ilse Van Criekinge) from connecting to her mailbox in online mode, the following single line needs to be run:
Set-CASMailbox -identity "ilse van criekinge" -MAPIBlockOutlookNonCachedMode:$True
To disable this for multiple users in one single line, you can first get all the mailboxes for which you want to disable the feature, and pipe that to Set-CASMailbox and set the value of MAPIBlockOutlookNonCachedMode to True. In the following example, all mailboxes located in the database called "Management" won't be able to connect using online mode.
Get-Mailbox -Database "Ex2007ee\SG_Management\Management" | Set-CASMailbox -MAPIBlockOutlookNonCachedMode:$True