It is possible to replace your Microsoft Lync client by a free IM client : Pidgin with a special enabled-plugin : SIPE
To download the latest win32 Pidgin version :
Download the SIPE plugin compiled for Windows :
Then, install your new IM client by launching the installer. Do the same for the SIPE client. Now, add your Lync account into Pidgin by providing the following information :
Protocol : Office Communicator
Username : your professional email address
Login user : your_firm_Active_Directory_domain_name\your_windows_login_name
and that’s all. For your first connection, you will be asked to enter your AD password and probably to accept some security certificates. No further configuration needed. It should work out of the box.

I get the following message:
disconnected
Authentication Failed
or
disconnected
Read error
Any ideas?
How did you set up the requested credentials?
Did you accept all the certificates given by Exchange?
Make sure that your AD login account does not get locked as well.
actually I’ve got the same, read error. there are workarounds for linux, but I am unable to solve it in Windows. all the setting looks good…
I got the “read Error” message as well; figured all the linux workarounds were based on an environment variable which theoretically would also apply in Windows. I fixed the issue by setting NSS_SSL_CBC_RANDOM_IV=0 (command line: “set NSS_SSL_CBC_RANDOM_IV=0″) before starting pidgin. worked like a charm.