Hmmmmmm ...............
Well, whatever the situation might be in reality, x-pstn-2strike: [number] still continues to be an undocumented feature so far as all publicly available postini data is concerned. I did raise the question of postini versions and updates etc ages back as well as identifying the relatively recent appearance of x-pstn-xfilter: header. I did also suggest that maybe it was 'old' information from a previous version of the system that was no longer relevant somewhere as well. But either way and whatever the real answer might be, something really does tell me that as also threatened ages back, I probably do indeed need to wheel out Mr.RTFM here in order to demonstrate 'best practice' in such situations rather than taking the suck-it-and-see, trial-and-error or we-have-always-done-it-so-it-must-be-right stylee approach

However, it is quite interesting that an example was apparently found during the Christmas break seeing that the latest release of postini documentation appears to be V6.12 dated 14th December which implies no formal changes since then. When was that message actually received ?
Of course, all this does raise yet another very serious potential issue. If postini can and do make random changes to fundamental headers willy-nilly then what exactly are PN going to do to ensure that such actions are not going to 'upset' their analysis and result in problems for customers ?
How are PN going to track and evaluate any changes that postini may make to their systems so that they can take appropriate action to ensure that customers don't get problems ?
How are such version changes or other tweaks announced and monitored ?
It would appear that some form of reliable configuration management is going to be pretty essential here to avoid customers experiencing problems that PN could and should have sorted way before they happened.