To resolve this issue on an Exchange 2010 server that is not hosting the Client Access server role, you must install a self-signed certificate. This certificate can be one issued by a certification authority server in your organization or one issued by a third-party certification authority.

If you cannot install a self-signed certificate on the Exchange 2010 server on the workstation on which Outlook is installed, you can use the following workaround. Install the self-signed certificate from the Exchange 2010 server to the Trusted Root Certification Authorities store on the workstation. To do this, follow these steps:

Start Outlook.

In the Security Alert dialog box, click View Certificate.

In the View Certificate dialog box, click Install Certificate.

In the Certificate Import Wizard, click on the Certificate Storage Wizard page to place all certificates in the following stores Put both and click Browse.

In the Select Certificate Store dialog box, click Trusted Root Certification Authorities, and then click OK.

Click Next on the Certificate Store wizard page

Click Finish to complete the wizard.

When you click Yes you are prompted to confirm the installation of the certificate.

When you click OK, it is recommended that the import has been successful.

Click OK to close the View Certificate dialog box.

Click Yes in the Security Alert dialog box to continue starting Outlook.

Exit and restart Outlook.

Now, you will not receive a security warning when you start Outlook.

After using this procedure to install the certificate you can confirm that the certificate is installed correctly on the client. To do this, follow these steps:

Start Windows Internet Explorer.

Click Internet Options on the Tools menu.

On the Content tab, click Certificates.

In the Certificate dialog box, click the Trusted Root Certification Authorities tab.

To find your server certificate scroll down in the list of installed certificates.

Note that in the following scenario where you are using a self-signed certificate on an Exchange 2010 server, Outlook does not display the security alert dialog box if both of the following conditions are true:

List this certificate

The date in the expiration date column has not yet arrived