Extended Validation SSL Certificates, also known as EV Certificates, provide the strictest validation requirements to prove to your customers that your site is not a phishing or fraudulent website, and that it's safe to proceed on your website.
2. Open the Properties for the Web Site that is hosting OWA (normally the Default Web Site)
3. Select the Directory Security tab and click Server Certificates
5. The Process a Pending Request dialogue box will appear (below), navigate to the site certificate that you received, and click Next
7. Click Next.
Install the intermediate certificate
You have now installed the SSL certificate into our web site. Next, you’ll need to enable SSL for OWA.
2. Select the Directory Security tab and the click on the Edit button in the Secure Communication section
4. When users enter http://ahost.adomain.com/exchange, they will receive an "HTTP 403.4 - Forbidden: SSL required https://ahost.adomain.com/exchange.
5. Please see the Microsoft article regarding forcing the use of SSL with OWA: Click here
6. Finally, ensure that your Firewall is configured to allow HTTPS (port 443 by default) to pass through