Question: Do I need to include the Autodiscover names for all of my domain names in my SSL certificate?
- Do I need to add the Autodiscover name to my SSL certificate?
- Do I need an Autodiscover name for all of my SMTP domains in my SSL certificate?
Both questions can be answered easily once you understand the basics of Autodiscover.
Put simply, Autodiscover is a service hosted on Client Access servers that Outlook 2007 and 2010 clients can use to automatically discover information about the Exchange environment.
An example of Autodiscover in action is when a mailbox-enabled user launches Outlook 2007/2010 for the first time and the Outlook profile is automatically configured with the correct Exchange server name for that mailbox user.
For internal, domain-joined clients this involves looking up the Autodiscover SCP (Service Connection Point) for the AD Site that the user's computer is in. Or if no SCP exists for that site the SCP in another site will be used. This is configurable and is known as Autodiscover site scope.
The SCP is returned as a URL. This URL will be one of the Client Access servers in the organization, and will look something like this:
Get-ClientAccessServer | fl name,autodiscoverserviceinternaluri
Name : ESP-HO-EX2010A
AutoDiscoverServiceInternalUri : https://esp-ho-ex2010a.exchangeserverpro.net/Autodiscover/Autodiscover.xml
So for an internal, domain-joined computer the SSL certificate must include the name (or names, if more than one exists) for the Client Access servers in the organization that a client will be discovering via that SCP lookup.
Externally connected clients are different, because they can't lookup the SCP in Active Directory from outside of the network. These clients might be roaming laptop users with Outlook, or they might be ActiveSync capable smartphones such as iPhones. In either case they will attempt to connect to Autodiscover by performing a DNS lookup for “autodiscover.smtpdomainname”.
For example an iPhone user setting up their Exchange mailbox will enter their email address (eg [email protected]), user name and password. The iPhone will then attempt to autodiscover the Exchange server by looking up “autodiscover.exchangeserverpro.net” in DNS. If it can resolve that name it will then connect to https://autodiscover.exchangeserverpro.net/Autodiscover/Autodiscover.xml to retrieve Exchange server information.
So for an externally connected client the SSL certificate must include the autodiscover.exchangeserverpro.net name, or optionally the “exchangeserverpro.net” name if you don't configure an “autodiscover” name (though I recommend you do, as often the domain name on its own resolves to a different IP address such as the web server that hosts the company's website). Naturally that name must also be in your public DNS zone.
Now that you can see that you need the “autodiscover.smtpdomainname” name in the Exchange 2010 SSL certificate the final question is whether you need to include autodiscover names for all of your SMTP domain names.
The answer is that you will only need an autodiscover name for each SMTP domain that a user is likely to enter as their email address (eg in the iPhone example above). So for most organizations this means any domain names that are used as primary email addresses for mailboxes. Any additional domains that may be legacy names from a previous company name or a merger can probably be left out of the certificate.