I had to migration RightFax from the H323 into SIP and spent some time on this. The procedure is pretty strength forward, but one thing is good to know: changed the Media Renegotiate Delay Outbound from -1, which means Rightfax does not initiate T.38 but waits for the other side to initiate it, to 2000 which means that Rightfax initiates T.38 switchover after 2s.
Without this setting I got the following Fax Receipt Error : “An incoming fax could not be received because a proper connection with the sender’s fax machine could not be established.“
Here it is!!
Don’t forget to check the CUCM SIP Trunk and inbound CSS!:)