Please follow these instructions to install your SSL certificate on Microsoft Outlook Web Access:
Install your SSL Certificate
1. Once you received your SSL certificate by e-mail, please copy and paste it into a text file (with Notepad or Wordpad) and save the file with the .crt extension. (Include the tags -----BEGIN CERTIFICATE----- and -----END CERTIFICATE-----).
2. Open Internet Information Services Manager (IIS).
3. Expand Internet Information Services if needed and browse to the Web site you have a pending certificate request on. Right-click on the web site and click Properties.
4. Click Server Certificate under the Secure Communications section in the Directory Security tab.
5. Click Next. Choose Process the pending request and install the certificate. Click Next.
6. Type the full path and filename of your .crt file (from step 1).
7. Verify the certificate details and click Next.
8. Click Finish.
Assign your SSL certificate in Exchange
1. Using Internet Information Services Manager, open the Properties for the Exchange Virtual Directory.
2. Select the Directory Security tab, click Edit in the Secure Communication section.
3. In the Secure Communications dialogue box, check the box Require Secure Channel (SSL), you could also check the box Require 128-bit encryption, if you do check the 128-bit checkbox, any browsers that do not support 128-bit encryption will be unable to connect to OWA. Now when users enter http://www.yourdomain.com/exchange, they will receive an “HTTP 403.4 – Forbidden: SSL required Internet Information Services” error message, because we have configured OWA to require SSL. SSL uses the HTTPS protocol, so users would need to enter the url as https://www.yourdomain.com/exchange.