The Exchange Server Recipient Update Service (RUS) is important to the overall health of your messaging environment.
In small organizations, the RUS often stays in the background.
However, if you work with large or complex deployments, you're likely to find yourself trying to cope with multiple recipient policies or wishing you understood why the RUS doesn't do quite what you'd expect it to do.
The RUS searches for Active Directory (AD) updates on a scheduled basis, then takes action to ensure that the objects it finds can receive email.
When you edit a mail-enabled object's properties and select the Automatically update e-mail addresses based on recipient policy check box (on the E-mail Addresses tab of the object's Properties dialog box), as Figure 1 shows, the RUS determines which recipient policy to apply to the object, then carries out the instructions that the policy contains.
Some deployments, such as hosted application service provider (ASP) or ISP installations, opt not to use the RUS to generate email addresses.
Instead, these organizations, which often have a multiplatform directory-provisioning and -synchronization process in place, might choose to use a third-party program or utility.
This approach is acceptable as long as the chosen program updates AD with the information necessary to let Exchange route and deliver messages.
Exchange creates a default recipient policy when you install the first server in an organization.Because SMTP is the basic routing mechanism for Exchange, this default policy ensures that every mail-enabled object has an SMTP address and uses the format mail [email protected](where is derived from the AD forest that contains the Exchange organization).The value of the mail Nickname attribute is unique within an organization, so this policy is sufficient to generate unique email addresses.Small organizations might decide to leave the default policy in place, but most large organizations prefer to follow the generally accepted [email protected] format for SMTP addresses.You can easily create a new recipient policy to instruct the RUS to create addresses in that format, then give the new policy precedence over the default policy so that the RUS processes the new policy's instructions first.Note that Microsoft recommends that you create a new policy rather than change the default policy (for reasons mentioned in the Microsoft article "How to customize the SMTP e-mail address generators through recipient policies" at This is good advice: Clearly separating organization-specific settings from default values is always a wise approach.