Exchange 2010 – Setting up email disclaimer via OU

I need to set up an email disclaimer for multiple users in an organisation running Exchange 2010. I have looked at implementing a transport rule via Distribution Groups but it can be messy as the group closest to being relevant would include some people who shouldn’t be included and exclude people who should be included. Instead of adding people in manually and creating exceptions, is there another way via OU? Cheers

ZE