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.
(cherry picked from commit 01dc322aebcff0e8075c54f81eb7d171a32fb9e7)
Replying to a thread whose last message I sent addressed the reply to me:
Reply put my own address in To, and Reply all put me in To with everyone
I had actually written to demoted to Cc. Following up on your own last
message is an ordinary thing to do, and this made it useless.
There was already a guard for exactly this, and the guard was sound. What
it rested on was not. It asked whether an address was in the identity
list, and that question has a wrong answer in more situations than it has
a right one:
- the list is empty until identities load;
- an alias or a shared mailbox is not in it at all;
- it compared lowercased strings with `includes` where the rest of the
codebase uses `sameAddress`, so an identity address stored with
whitespace was enough to break it;
- the check ran on the address the reply was about to go to rather than
on the sender, so a message of mine carrying a Reply-To skipped it
entirely and my reply went to my own desk;
- and the Reply all branch never filtered my own address out of To, though
the Reply branch did.
Every one of those failed silently, which is why five of them accumulated.
So the folder is asked first: a message in Sent is mine whatever address
it went out as, and `mailboxIds` is already fetched in LIST_PROPS with
roleId("sent") on the mail store, so this costs no request. The identity
list stays as a second opinion, now compared with `sameAddress`, and the
whole test keys off the sender rather than off the computed recipient.
Two cases remain unanswerable and are commented rather than papered over:
a message from an unlisted alias that is not in Sent either, and any
message at all when identities failed to load and it is not in Sent.
Neither signal exists. Both are far narrower than what was broken.
Reply addressing had no tests at all, which is how a guard this
load-bearing came to be wrong five ways at once. Fifteen now, seven of
which fail against the old code.
jcoffey
jcoffey-dev