"Firmware release 8.1(1b) is designed and tested to interoperate with Cisco call control, most notably Cisco Unified Communications Manager releases 6.0 and 5.1. Although SIP firmware is IETF RFC 3261 compliant, it is not supported by Cisco TAC or Engineering for
use with non-Cisco call control systems."
So this phone is SIP compliant, is up to the customer to test it with 3rd party call control. It should be similar as to how you configure a 3911 with CUCM:
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...