Exchange 2010/Outlook 2010 Security Alert (...there is a problem with the site's security certificate.)

Question

I've been looking to resolve this issue for a while now and was hoping someone could help me understand my options.
We have Exchange 2010 & Outlook 2010 in our environment. I've created a SSL cert for our ActiveSync from a reputable CA and unfortunately, as you may not be surprised, we are seeing an alert each time we open Outlook that states:
"Security Alert; Information you exchange with this site cannot be viewed or changed by others. However, there is a problem with the site's security certificate.
The name on the security certificate is invalid or does not match the name of the site."
Of course my internal server name does not match my external server name. So the SSL I had created for use with OWA and ActiveSync is rejected by my internal Outlook clients.
After doing some research I believe this is related to the Autodiscover service being configured with my internal server name and not my external name. 
I've found some info about adding New-AutodiscoverVirtualDirectory and Set-ClientAccessServer commands and then found this article that might help.  (Configure
Outlook Anywhere to Use Multiple SSL Certificates) but nothing is specific to my configuration and I'm concerned about what will happen to my existing configuration if this fails. 
What happens when you run Set-ClientAccessServer? Does it retain and keep the old server config in place and add a new one or does it wipe it out? Will all of my devices need to be reconfigured?
Same with New-AutodiscoverVirtualDirectory.  Does this simply add another virtual directory or is it going to overwrite my existing config?
Then there is the question of whether or not any of this will actually address my issue at all.
absolutezero273c

Answer 1

Sorry.
"[PS] C:\Windows\system32>Set-ClientAccessServer -Identity MailExt -AutoDiscoverServiceInternalUri "https://MailExt
.contoso.com/autodiscover/autodiscover.xml"
The operation couldn't be performed because object 'MailExt' couldn't be found on 'DomainController2.contoso.local'.
    + CategoryInfo          : NotSpecified: (0:Int32) [Set-ClientAccessServer], ManagementObjectNotFoundException
    + FullyQualifiedErrorId : 4D980455,Microsoft.Exchange.Management.SystemConfigurationTasks.SetClientAccessServer"...is the error I get.
I've created the split zones and populated the Forward Lookup Zones as follows:
CONTOSO.COM
MailExt(CNAME)MailInt.contoso.local
_tcp _autodiscover(SRV)MailExt.contoso.com
CONTOSO.LOCAL
MailInt(A)192.168.1.10
MailExt(CNAME)MailInt.contoso.com
One thing I did notice is that there isn't a _tcp _autodiscover entry for MailInt in my Forward Lookup Zones.  It was recommended that I make that entry for _tcp _autodiscover(SRV)MailExt.contoso.com in another post I read somewhere.
I believe what I am trying to do is create a new autodiscover object as is shown here:
I see there is a Get-ClientAccessServer & Set-ClientAccessServer command but I need to add a CAS. Does the Set-ClientAccessServer add or simply modify?
Or would that require the New-AutodiscoverVirtualDirectory command? I read
this page that discussed creating new virtual directories but that seemed a little risky without knowing all the ins and outs of how this service functions and to what degree this would affect the existing configuration.
I was able to use the Set-ClientAccessServer command and change the actual internal autodiscoverUri to https://MailExt.contoso.com/autodiscover/autodiscover.xml but the name still says MailInt and I continue to get the SSL cert warnings because it is looking
at MailInt.contoso.local.
absolutezero273c