Customize SMTP Email Addresses by Recipient Policies

Using Recipient Policy in Exchange Server we can define the SMTP namespace that our mail system accepts emails from as well as the way email addresses are generated for each individual recipient. Basically the format that is used in recipient policy is @domainname and no control over individual email addresses is given by default. To customize and define the email alias scheme we can provide some arguments like %s (surname) and %g (first name). This means I can define a naming policy for generating email aliases using firstname and last name combinations. Lets take a look at some examples:
1)The SMTP namespace is "itbuzzer.net" and alias should be generated in "Firstname.Lastname" format: %g.%s@itbuzzer.net --> saeed.pazoki@itbuzzer.net
2) The SMTP namespace is "itbuzzer.net" and the policy should use the users Firstname plus the first 3 letters of the Lastname: %g%3s@itbuzzer.net --> saeedpaz@itbuzzer.net
Microsoft emphasizes that this replacement arguments should not be used in the default recipient policy and a new recipient policy should be created to prevent problems.
In the following KB more replacement arguments are explained:
822447 - How to Modify an SMTP E-Mail Address by Using Recipient Policies