[Users] BCP: rewrite every header?

I just debugged the following: A PSTN gateway we use is completely non-responsive when the INVITE has this: From: Mark Kent (desk) <sip:markkent@sip.example.com>;tag=foo Contact: Mark Kent (desk) <sip:markkent@192.0.2.216:5060> but things work OK for this: From: "Mark Kent (desk)" <sip:markkent@sip.example.com>;tag=foo Contact: "Mark Kent (desk)" <sip:markkent@192.0.2.216:5060> and also for this: From: Mark Kent <sip:markkent@sip.example.com>;tag=foo Contact: Mark Kent <sip:markkent@192.0.2.216:5060> Now, I know that the EndUser box should put quotes in there to be safe. RFC3261 says "special characters MUST be in a quoted string to be used within a parameter value." But that's not the point of this post... the point is, should I be rewriting every header? Is that standard practice? BTW, I have the same hangup with the SJphone softphone, but there I think it's because of this: From: "Mark Kent(mac)"<sip:MarkKent@sip.example.com>;tag=foo See, no space between the double-quote and the left-angle-bracket. So, should I be re-writing headers to present a single face, independent of the EndUser boxes, to external SIP gateways? Thanks, -mark P.S. FYI, the box that is not putting in the quotes is a SPA3000 running 3.1.10(GWd). A SPA942 running 4.1.10(e) puts in the quotes.