I have a 3rd Party certificate been working for at least 2 years on Exchange 2007 and does not expire for another year and the above error message appears when access via Outlook 2007 PC Anywhere. I have checked the settings of the certficate using the link http://support.microsoft.com/?kbid=940726 on the exchange serevr. I can confirm all settings have my external address. My internal domain is different to my external FQDN used for the certificate. My internal DNS as a primary zone for my external domain with A host record point to the internal IP of Exchange server. My External DNS as a A record for autodiscover pointing to its external IP address for the server and a SRV record. Any ideas as to way all of a sudden I'm getting prompted with the certificate error message? Philip Walker

Are you sure that it is your certificate that is generating the message? When you get the prompt you should be able to view the certificate. The most common cause is autodiscover. That process will query a number of URLs, including https://example.com/ . Now if your public web site is on a host where they are sharing the IP address with other web sites and they have put an SSL certificate on to that IP address for another host name, the error can be generated. Looking at the certificate is key. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources

Yes, When I view the certificate when it promts it is the correct name. If I use the exchange OWA thete is no certificate error....... Only 1 exhange server in site and using only 1 IP address. Philip Walker

Does the issue happen to all users? Does it happen to the clients that connect to server from inside the local network? The issue is typically about the user is trying to access server by using a name that isn’t on the certificate. Please check if there’s any incorrect entry in the hosts file on the problematic workstation, any proxy setting in the internet explorer Please run “Test E-mail AutoConfiguration” on the problematic outlook client, and then check the output Please run Remote Connectivity Analyzer to check outlook anywhere procedure James Luo TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.