sundance-communications.com/forum Forums TDM Business Telephone Systems Avaya - Lucent Telephones & Systems IP Office getting voice mail remotely

There is no 5.1 Where are you loking for that number?
If you look at the Manager, it would be in Help>about. But that is just the software of the management.

If you go into the config, under control units you will see the actual release for the hardware.