Microsoft has released (sometime ago) an online tool to check your Internet connection compatibility with Online Services (messaging and collaboration [Exchange, Lync…]).
This tool is available at the following URL http://speedtest.emea.microsoftonline.com/
There is some specific communication ports to be open in order to allow complete test:
- classical one: HTTP port (80)
- additional ones: UDP 8090, TCP 20000 and TCP 20001
If you don’t open these ports, you will have an incomplete test and report (like the following one)
Once these ports are open, you have a full test and report
Anyway, according to Microsoft Online Support team, this can be forgotten
Thanks to Arnaud Alcabez for the information 