[ih] installled base, IPv8...

[John Levine]

It appears that Dave Crocker via Internet-history <dhc at dcrocker.net> said:
>Old protocols never die and they don't fade away.  Contrary to wishful 
>thinking.  The power of an installed base, at Internet scale, is not to 
>be trifled with.
>
>By way of offering an obscure example of this reality, take a look at 
>the 'obsolete' construct in 
>https://www.rfc-editor.org/rfc/rfc2822#page-29. Note that it has been 
>retained in later revisions.  Because usage of those components persists.

I suspect a fair number of those obsolete constructs are not used at a
detectable level in current mail. But there isn't any good way to find
out short of turning them off and see who complaints. In this case the
cost of keeping the obsolete features is low, while the potential cost
of dropping them if we guessed wrong is not.

R's,
John