EDIT 03/26/08: Please see our later post on this subject for the location of updated prerequisite check XML file.
Summary
This is a follow-up to an earlier post: Single-label Domain Names and Exchange Server 2007 SP1. Please refer to it for background information on this issue.
After investigating Exchange 2007 Service Pack 1 installed in an Active Directory domain with a Single-label Domain (SLD) name, Microsoft has changed the Setup prerequisite rule for SLDs from an Error to a Warning, thereby allowing Service Pack 1 installation to continue in SLD environments.
There are a few items that I want to point out:
We have the following recommendations for customers who have Exchange installed in an SLD.
If you have Exchange 2003 installed in an SLD, and you have not run any Exchange 2007 Setup /prepare switches yet:
If you have Exchange 2003 installed in an SLD you should change your domain name to a fully qualified domain name (FQDN).
Exchange 2007 RTM is installed and you want to migrate to a supported configuration:
If you want Exchange 2007 deployed in a fully supported configuration, then you have two options:
Please note that if you have already installed Exchange 2007 into the organization containing Exchange 2003, or if you have already run the Exchange 2007 /prepare setup switches, you cannot perform a domain rename even if Exchange 2007 servers are removed from the organization. That is because Exchange 2007 setup creates new Active Directory objects which will not be properly renamed by the Exchange 2003 domain rename fixup script.
Microsoft is changing the Single-label domain pre-requisite check from an Error, which blocks Setup, to a Warning, which cautions you strongly, but allows Setup to proceed. While the exact wording has not been determined, it will be similar to the following: "Setup has determined that this computer belongs to a domain that has a single-label DNS name. This is not a recommended configuration. You should plan to migrate to a fully-qualified domain name. ". We'll inform you when this rule has been changed, and when the update is available for download.
If you are installing Exchange 2007 SP1 from files on the local computer, and the computer is connected to the Internet, Setup will automatically download the new rule when it is available.
In addition to the prerequisite rule change, we're also going to modify the ExBPA Health Check rule to mirror the modified Setup check.
Some other things that you should be aware of include:
Installing from DVD If you are installing Exchange 2007 SP1 from a DVD, Setup will not download the new rules. In this scenario, you must copy the Setup files to your local computer and then run Setup from those local files. This allows Setup to download new rules.
Computer not connected to Internet If your computer is not connected to the Internet, it won't be able to download the new ExBPA rules. To workaround this, Microsoft will make the updated XML file available for download. Customers will need to download the update and then manually update their local installation files. Details on how to obtain the new XML file will be announced at a later date.
Autodiscover won't create profiles correctly without a hierarchical address This issue should only apply to customers that are only sending mail internally; anyone who is routing mail externally should have encountered and resolved this issue. Outlook assumes that the default Email Address Policy (EAP) would be to a publicly resolvable name. To send mail on the Internet, SMTP domains in an EAP must resolve to one of the top level domains supported by RFC's. The technical requirement for Outlook to work is that the EAP represents at least two levels of hierarchy in the name, i.e. it must have at least one dotted suffix. The following would be examples of names that Outlook would consider valid:
The thing to note here is that although Outlook will consider contoso.test to be a valid domain name, it is not publicly resolvable according to RFC standards because there is no top level domain called ".test" on the Internet. Such a domain name could be used internally, however, mails would only route internally. It would not be possible to receive mail for that domain from outside the company.
To maintain your SLD, your default EAP must be set to include at least two levels of hierarchy, for example:
Fname.Lname@contoso.com
If you have a mixed environment of Exchange 2003 and Exchange 2007 the EAP is probably the Exchange 2003 version and won’t have the opath filter syntax, therefore run both of the following cmdlets in order. If you have a pure Exchange 2007 environment just run the second cmdlet:
Set-EmailAddressPolicy "Default Policy" -IncludedRecipients AllRecipients
And then:
Set-EmailAddressPolicy "Default Policy" -enabledPrimarySMTPAddressTemplate "%g.%s@contoso.com"
Domain Rename - best option (if you can use it)
Microsoft strongly recommends that you move off of your single-label domain and transition to an Active Directory domain with a fully qualified domain name. Some of the other challenges with this configuration include:
Microsoft would like to take this opportunity to make an additional suggestion to customers who fit both of these criteria:
and
Customers who fit both of these criteria face two upgrades, both of which call for the removal of Exchange 2007 prior to continuing.
We suggest that you plan your next operating system and Exchange Server upgrades to resolve both of these issues at the same time by either migrating objects to a new domain with a fully qualified domain name, or by performing a domain rename of your existing domain.
- Ed Beck