miconda left a comment (kamailio/kamailio#4148)
The R/From/To-URIs should have the domain (or the IP) of the SIP server, in most of the cases it is a value that has to be known by both sides of the call.
In case of interconnect routing when From/To-URIs have different domain/ip, there are functions offered by uac module that can be used to change (and revert) them.
Also, there could be other headers that might need to be updated, specific per CPE/SIP-phone, functions from textops/x modules can be used to manage the header values.
The design for topoh/topos targeted to take care of the request/response routing header (via, route, record-route, contact). The other headers have to be dealt with config operations. If you want to discuss more on this topic, use the sr-users mailing list.