It is possible to use Reuters Messaging from Linux and it is actually very easy with a few pointers. I need to add the standard disclaimer at this point that this website and what follows is in no way endorsed by Thomson Reuters, Microsoft, Ubuntu or any other maker of the applications used and that you follow at your own risk.
The first thing to realize is that it is not, at least currently, possible to log into the Reuters Messaging network using the default Empathy Instant Messaging client installed with recent versions of Gnome and Ubuntu 10.04
and later. Instead you will need to install Pidgin, which given its versatility, cross platform capabilities and large amount of available plug-ins is a really useful instant messaging client. You will also need to install the Pidgin SIPE Plug-in for OCS as the solid implementation of the SIPE plug-in by Anibal Avelar and all is what really makes this possible. Both can be downloaded from those links but the easiest way on Ubuntu is to just go to the software repository and install them that way.
Applications -> Ubuntu Software Center Search for Pidgin and Install
Search for Pidgin SIPE and install
Applications -> Internet -> Pidgin Internet Messenger
What follows would actually work from Windows as well as Pidgin is cross platform but I am assuming most people would be using the official Thomson Reuters Messaging client rather than Pidgin on Windows so I will stick to using Ubuntu Linux for the explanation. When setting up your new Pidgin account for Reuters messaging the Protocol should be Office Communicator, which will only be available if the Pidgin SIPE plug-in for OCS is already installed. In my case Username needed to have the E-mail address modified to change the @ to a . and add @reuters.net at the end like this firstname.lastname@example.org. You should have been given this info when you received your Reuters IM account but if not you can check on a working Windows version of RM by looking at Tools -> Preferences -> Connectivity and then unchecking Use the simple login screen. Login is straight forward E-mail address and your Password is the password they gave you for Reuters Messaging (not your Windows login). If you don’t have your password you will need to have it reset and sent to you.
Accounts -> Manage Accounts -> Add
Server[:Port] should be either your corporate Reuters proxy or for an external connection sip.reuters.net:443. Connection type must be SSL/TLS. Do not select Kerberos but do select Single Sign-On.