Domain user account: Learning Stuff Primary email address: learningstuff@yourdomain.com Aliased SMTP address tied to mailbox: alias1@yourdomain.com Scenario: You want to build client side Outlook rules based on the email address contained in the message header. When the header contains alias1@yourdomain.com your rule moves the message to the ‘Alias’ folder that you’ve created within your mailbox. Situation: Send an email from Learning Stuff’s Outlook profile to alias1@yourdomain.com. When the Outlook client (2007 or 2010) is set to cached mode the rule works. When the Outlook client is not set to cached mode the rule does not work. Findings: Email headers have changed based on how Learning Stuff’s Outlook profile is configured. Cached mode will show the actual TO email address (alias1@yourdomain.com) within the email header. Non-cached modes will translate messages sent TO alias1@yourdomain.com to learningstuff@yourdomain.com within the email header, which in turn breaks the client side email header rule. Thoughts: Call me crazy, but this seems like a bug. Email headers should not change based on a cached client vs a non-cached client! Stranger yet, if using webmail to send your own alias a message, the email header will always only contain your primary email address. In other words, when using outlook in cached mode to email your alias, the message header will contain one set of data – use webmail and the header contains something different. Is this because webmail resolves the alias to the primary email address as soon as you click send but before the message is actually sent? Maybe Outlook resolves aliases this same way when not in cached mode? Due to this feature it makes client side rules based off of an email alias wtihin a message header compelely unreliable. Mr. Schultz PS: I have vetted this against SBS 2008 (Exchange 2007) & in an enterprise domain environment using Exchange 2010 SP1; Outlook 2007 and 2010 clients.