For a description of Single Label Domains, see the Single Label Domains topic in the Microsoft DNS Namespace Planning Solution Center.
Single Label Domains
Disjoint NamespacesFor a description of Disjoint Namespaces, see the Disjoint Namespaces topic in the Microsoft DNS Namespace Planning Solution Center.
Discontiguous NamespacesFor a description of Discontiguous Namespaces, also known as noncontiguous namespaces, see the Discontiguous Namespaces topic in the Microsoft DNS Namespace Planning Solution Center.
Microsoft Office Outlook
Single Label DomainsBecause the use of SLDs is not a recommended practice, Office Outlook versions are not extensively tested in this scenario. Therefore, there may be incompatibilities when Office Outlook is implemented in an SLD environment. Although users can install Office Outlook 2007 or Office Outlook 2010 on SLDs by using workarounds on the Exchange server side, SLDs produce non-RFC compliant email addresses.
Note Any workarounds may not be supported scenarios and have not been confirmed or tested by Microsoft. Use the following information at your own risk. Microsoft provides this information "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.
Office Outlook has checks and balances in place to maintain RFC compatibility. There is the ability to support SLD server environments with an Exchange server as the back-end, while using domain joined computers with some server-side workarounds (for example, making the primary email addresses end in an RFC-compliant domain).
Based on the suffix of the email address that is provided, Autodiscover contacts a server. Because the email address must be RFC compliant, the email address has an FQDN suffix. If you are on a domain-joined computer, the Autodiscover server may be identified in Active Directory Domain Services (AD DS). In this case, an Autodiscover server that is identified in AD DS takes precedence over parsing the email address. However, on a computer that is not joined to the domain, the only source for the Autodiscover server is the suffix of the email address. If the computer is not joined to the domain, an additional workaround must be deployed to the client computer so that Autodiscover requests are redirected to an SLD-based server.
The ability to redirect clients by using a local Autodiscover override response is documented in the Outlook Automatic Account Configuration white paper.
POP and IMAP both seem to support SLD configuration scenarios in that no manual configuration overrides are required. However, automatic configuration will not work because we expect an RFC compliant email address in the Automatic Configuration dialog box.
Office Outlook 2010 has the following known incompatibilities:
- Users cannot add the SLD email address to the junk safe senders/safe recipients/blocked senders lists.
- If the manual, client-side redirection workaround that is mentioned in the Outlook Automatic Account Configuration white paper is not implemented, Autodiscover does not work on a computer that is not joined to the domain.
- Check Name does not recognize the SLD email address.
- Outlook does not accept SLD email addresses during account configuration.
- SLD: FreeBusy and MailTip do not work for an SLD account.