I have installed SCCM client on several workgroup and machines on separate domain to our SCCM infrastructure, with use of ports and certificates.
We find that SCCM seems to manage the clients fine, except that the Endpoint Protection appears to die some hours or days later - the definitions seem to fail to come down to the machine and ultimately the Endpoint icon turns red and shows it is turned off.
Software Updates via Software Centre are otherwise coming down to the machines without problems - if anyone has any suggestions on what could be causing Endpoint to fail to keep itself active, that would be helpful.