A website contact form mails the site's own address: From and To are
both info@thesite, and the person who filled the form in is in Reply-To.
Replying addressed the draft to info@thesite -- the site's own desk --
instead of to them.
The reply already knows two shapes. A message somebody sent me is
answered to its Reply-To, which is what that header is for. A message
*I* sent is answered to the people I wrote to, and deliberately not to
my own Reply-To, which is where answers to me belong and would send my
reply to myself. A contact form passes the test for the second: every
address in From is mine.
So it fell down the chain the second shape keeps for a message with
nobody obvious to answer -- To without me, then Cc, then, having run
out, every address on the message, which here was mine alone.
The Reply-To now goes in that chain, one step before the last: when no
recipient but me is left and the message names a Reply-To that is not
mine either, that address is who it is really from. Keeping it after the
Cc is what leaves a message I did send alone -- somebody I actually
wrote to still beats my own Reply-To, which is the case the existing
guard was built for and its test still holds.
No new strings.
jcoffey
01dc322aeb