Which SIP handsets are best for SCMC or SCME would one recommend? I am getting a lot of enquiries where the clients donot want to be vendor locked in and want to use any other SIPphones. I tried a YEALINK T58 as a SIP extension and its failing to dial out but its receiving. If I load it straight to the SIPserver it functions well.

I've used the gigaset ip cordless on acmc no issue.
Haven't tried yealink yet, but your issue is likely the dial plan needing to be configured in the handset.

Also ip5000 polycom works

thanks a lot. will try those 2.