When the user "sales" is created, at that moment there is no mailbox, just the user. In AD, there is a tick mark (sort of) saying this user gets an Exchange mailbox. When the Exchange recipient update policy runs is when the actual mailbox gets created. John T From: exchangelist-bounce@xxxxxxxxxxxxx [mailto:exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of Jabber Wock Sent: Monday, January 28, 2008 8:43 PM To: [ExchangeList] Subject: [ExchangeList] Puzzling Mystery: Ex2k3 allows adding a mailbox with same name as an existing SMTP alias! Hi, Here is a strange situation I ran into on an Exchange 2003 server and I was wondering if anyone can shed light on it. An existing user has email address Joe.Blo@xxxxxxxxxxxxxxx And he is also configured with an existing SMTP "alias" of sales@xxxxxxxxxxxxxxx So far so good, all is working great, for weeks and months. Now a request comes to make a mailbox for sales@xxxxxxxxxxxxxxx The admin does not realize that there is already a user with this same alias, and goes ahead and creates the new mailbox. Amazingly, and here is the perplexing part: Exchange 2003 and AD do not complain, but go ahead and allow this mailbox to be created! So now there is a mailbox named salesd@xxxxxxxxxxxxxx and also secretly and unintentionally, an existing user with an alias sales@xxxxxxxxxxxxxx ! And of course, any emails for sales@xxxxxxxxxxxxxx go to both. How and why does Exchange allow this? Interestingly, Exchange does not allow the opposite sitation. If I were to try and add sales@xxxxxxxxxxxxxx as an email SMTP alias to some other existing user Mary.Jane@xxxxxxxxxxxxxx, Exchange / AD refuses to do it as it correctly should. You may want to try this just as an experiment. So why is it allowed the other way? Is this an Exchange bug or a "feature" ? Best regards JW