Gotcha when adding Exchange transport rule disclaimers

Recently I was involved in a project to test outgoing e-mail disclaimers for only a specific group of users in our company.  Normally this would be a no-brainer using the standard features in Exchange transport rules to add a disclaimer using specific criteria.  However, while testing the disclaimers with a colleague, he observed that his tests worked fine when sent from a mailbox on Exchange 2007, but failed to work at all when coming from a mailbox on Exchange 2010.

So I began troubleshooting this issue and trying to find the cause of the problem.  In our company we actually have 3 generations of Microsoft Exchange running in a co-existence scenario (2003, 2007 and 2010 – with 2013 coming soon).  I tried everything I could think of to get the transport rule disclaimer to work, testing it on my own mailbox which is hosted on an Exchange 2010 server.  Sure enough the disclaimers did not work for my account.

I poured over KB articles and forum posts scouring the internet for any tips that might at least point me in the direction.  After several hours of searching I stumbled upon a forum post indicating that I should check the “remote domains” properties in the Exchange shell.  So I ran the command “get-remotedomains | FL” and sure enough the “isInternal” value was set to “true”.  Given that our transport rule disclaimers were conditional upon being sent to recipients who were “external” to our Exchange organization – of course none of the rules would work.

In order to resolve the issue, I ran the following command: “get-remotedomain | set-remotedomain -isinternal $false”

This allowed Exchange 2010 hub transport servers to recognize all email recipient domains not configured in our Exchange organization as “external”.  A second round of testing revealed that this change did in fact resolve the issue and the transport rule disclaimers worked perfectly for everyone, both Exchange 2007 and 2010 mailboxes.

I am amused and slightly annoyed that the vast majority of forum posts and KB articles I found about how to use Exchange transport rules to send outbound disclaimers has no mention of this possible “gotcha”.  I’m sure there are limited circumstances that would result in this issue which is probably why it was not mentioned in the articles I was reading, but I offer this as help to those who may face a similar situation.