How to Enable Outlook Web Access for Internal Clients Only
You can enable users in your corporate network to access Outlook Web Access, while at the same time denying access to external clients. To enable Outlook Web Access for internal clients only, you must create a new recipient policy and create a new HTTP virtual server.
After you complete these steps, users whose e-mail addresses do not have the same SMTP domain as the HTTP virtual server will not be able to log on and access Outlook Web Access. Also, if you do not use the SMTP domain as the default domain, external users will not be able to determine what the SMTP domain is because the domain does not appear in the From field when users send e-mail messages outside the organization.
Procedure
To enable Outlook Web Access for internal clients only
Create a recipient policy with an SMTP domain name. Users who are connecting to an HTTP virtual server must have an e-mail address with the same SMTP domain as the virtual server. Creation of a recipient policy is an efficient way to apply the same SMTP domain to multiple users.
Note
Outlook Web Access users do not have to know the name of the SMTP domain.
Apply the recipient policy to the user accounts for which you want to enable access.
Then, on the front-end server, create a new HTTP virtual server that specifies the domain that is used in the recipient policy.
For More Information
For detailed steps for how to disable Outlook Web Access for specific users, see How to Disable Outlook Web Access for Specific Users.
For information about managing and configuring Outlook Web Access, see the following topics: