🚀 go-pugleaf

In my opinion, the problem with "%" when used as an operator in
a mail address is that its meaning is not standardized anywhere,
to the best of my knowledge.  As long as this is the case, I will
avoid both using it and encouraging its use, which usually means
using the RFC822 "route-addr" form instead, inspite of its problems.

As background for your thinking:

Thanks to RFCs 822 and 976, the mail address operators "!" and
"@" have a defined meaning and precedence in relation to each
other:  at least for internet hosts, "@" has the highest
precendence.  Where does "%" fit in relative to "@" and "!"?  To
make a concrete example, given an address like:

			a!b%c@d
	
What path should the mail travel?  Assuming that "a", "b", "c", and "d"
are suitable single host or user names,  your answer should be of the
form:  The mail should first be delivered to host _?_, then to host _?_,
finally to host _?_, where it should be delivered to user _?_.

There are 24 different orderings of "a", "b", "c", and "d", but
probably you will think one of these three is the right one:

	1)	-> host a -> host d -> host c -> user b.
	2)	-> host d -> host a -> host c -> user b.
	3)	-> host d -> host c -> host a -> user b.

If you try to use an address like "a!b%c@d", and discover that the
mail is undeliverable, and you suspect the problem is that one of
your neighbors is doing something wrong, how do you get the problem
resolved?

-Larry Parmelee
parmelee@cs.cornell.edu