I have four users out of about 130 with the following problem. When they send an email to someone outside of our Exchange 2010 domain, the message gets stuck in outbox. This happens when they are using Outlook 2007 on 2008 R2 RDS, roaming profile, and redirected services. OWA works fine. Using a standard workstation works fine with same roaming profile and redirected folders. Safe mode works for two of the users. Also works if a user does a right-click to send a file as an attachment instead of opening new message and adding file. Deleting roaming profile works for a short time. One user has rare occurrence when email get sent correctly. All users have same configuration.