If you need to inter-operate with an MS environment, and they have a Microsoft Office Communications Server, you can quite easily do so using pidgin-sipe.
I just packaged pidgin-sipe for Mandriva, it should be available in Mandriva 2010.0 (in contrib), and I uploaded to contrib/backports for 2009.1.
To use it, create a new account of type “Office Communicator”. It seems you need to set “Username” as your “Exchange” email address, and the login in DOMAIN\username or username@DOMAIN.COM format (IOW, NT username or Kerberos Principal). Do set the “Local alias”, as it seems this is what you will be seen as by the other participant (and no, it is not filled if you don’t enter it yourself).
So far it seems only IM works, no VOIP or video conferencing. Since MS OCS is just SIP over TCP, it may be possible that other SIP clients could do VOIP or video conferencing, but my 2 minutes with ekiga did’t result in any success. There is a bug filed on kopete to add support for SIP over TCP, but so far not much action on it.
Pidgin also supports bonjour chat (if you install the pidgin-bonjour package), for easy server-less IM with other pidgin users, or users on Mac OS X. More on this later
On my corporate windows box, on which I don’t have privileges to install any software, I have no client that is able to connect to the OCS server managed by the same people who manage my desktop. MSN Live messenger, which MS really wants you to use (preventing it from auto-starting is non-trivial) doesn’t seem to support MS OCS server.
One wonders if they really are trying to compete or not, as the MS Office Live Messenger client can apparently be used with an asterisk server. Once I have the client, I might try …
