I came across an issue where the email message sent from OWA 2003 using IE8/9 (while co-existing with Exchange 2010) delivers a lot of garbage as the message body. This only happens if you have a 2010 transport rule for disclaimer.
The below screenshot shows the type of email you get as a recipient.
It looks like it is a known issue and the KB article explains the issue. The problem occurs because Outlook Web Access for Exchange 2003 sets an email to an incorrect character set. When the message is routed by the Exchange 2010 server that has the disclaimer rule enabled, the email is converted to incorrect HTML tagging based on the incorrect character set. Then, the message is corrupted by the incorrect tagging.
The fix is to install a hotfix on Exchange 2003 servers in the environment and a registry edit to enable the hotfix. The server needs a restart as well.
This issue only happens while using IE. Firefox & Chrome works fine. Another reason to start using Chrome