I am having issues with Microsoft OCS 2007 where the service expects the tel uri to be in the e.164 format with +<number>. The 3CX doesn't doesn't like the use of the + and OCS 2007 requires it for reverse number lookup to a user account. I tried replacing the + with a '00' but no joy. 13:18:41.946|.\Endpoint.cpp(197)|Critical0|Endpoint|Endpoint::findSource:[CM010001] Line configuration does not allow identification of the source of this call. Check Advanced Options for Gateways and Providers and match a field to a correct value from the following: Contact IP: 'UMOCSMED.UM.LOCAL'; From: '+243'; To: '235'; Rline: '235'; Contact: The 3CX version is 3.1.2434.0. Is there any way to get the two systems talking?