Configurng the email address generator through Recipent Policies in Exchange Server 2003.

The Recipent Policies in the Exchange 2003 Server generates the email address of the users you create in Active Directory Users and Computers. For example users_name@domain_name.com.

When configuring a new Exchange server it is recommended that a new Recipient Policy be created, instead of using the Default Policy. Here is how you can configure or change the recipent policy.

The below is an excerpt from Microsoft Tech Net.

To modify any recipient policy:
Start Exchange System Manager.
Click Organization, click Recipients, and then click Recipient Policies.
Double-click the policy that you want to change. If you are going to generate your SMTP address by using the replacement strings listed below, do not modify your Default Policy. You may encounter problems if the Default Policy is based upon attributes such as Given Name or Surname.For additional information, click the article number below to view the article in the Microsoft Knowledge Base:
271339 (support.microsoft.com/kb/271339/EN-US/ ) XADM: Cannot Mount Database and Event ID 9546 Occurs
Click the E-Mail Addresses tab, and then edit the appropriate SMTP Generation rule by using the following switches.

The default format is:
user_name@domain_name.com
The following replacement strings are available:
%s = surname (last name)
%g = given name (first name)
%i = middle initial
%d = display name
%m = Exchange 2003 or Exchange 2000 Alias
%rxy = Replace all subsequent characters x with character y in username. If x = y, then the character will be deleted.
You can place a number in front of any of the preceding switches to define how many characters of the switch should be used, for example:
%1s = Uses the first letter of the surname
%5g = Uses the first five letters of the given name
NOTE: Invalid characters (in accordance with Request for Comments [RFC] 821/822) are removed from the user’s name.
More Information on the %r Replacement String
If a %r is used for the purpose of substituting a valid character for an invalid character, the entire %r string is ignored. Additionally, %r should be used immediately before replacement string where you want to replace characters.

Therefore, in cases in which you want to replace character “x” with character “y” in the last name (represented with %s) an SMTP e-mail address is generated as follows:
%g.%s
The proper use of %r replacement string is:
%g.%rxy%s
Putting %rxy in front of the whole e-mail will not work properly in the above case and will not replace character “x” with “y” in the last name.

NOTE: When using the %rxy string, x can equal blank space. This string can be used to merge spaces in the name with a valid character.

NOTE: You cannot use the %rxy string as %r to remove manually typed periods from the Initials field in Active Directory Users and Computers. We recommend that the manually typed period be removed from the Initials field in Active Directory as this also affects other attributes.
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Examples for User Logon Name = “AndrewLin”
Display name = “Andrew Lin”
Surname = “Lin”
Given name = “Andrew”
Format string SMTP address generated for sample user
————- ————————————–
%d@microsoft.com HollyEBarrett@microsoft.com
%r._%d@microsoft.com HollyE_Barrett@microsoft.com
%r..%d@microsoft.com HollyE.Barrett@microsoft.com
%g.%s@microsoft.com Holly.Barrett@microsoft.com
@microsoft.com HollyB@microsoft.com
%1g%s@microsoft.com HBarrett@microsoft.com
%1g%4s@microsoft.com HBarr@microsoft.com

282314 (support.microsoft.com/kb/282314/ ) Site addressing generates incorrect SMTP address for “%g.%s.%m”