Two halves of one rule: the address someone typed is theirs to keep, and it must be
the one that gets them back in.
A plus-tagged or dotted Gmail is often a deliberate choice -- registering as
me+siftlode@gmail.com is how you find out later which site leaked your address. The
Google callback overwrote it with the account's primary, which can never contain a
'+', so the tag vanished on the first Google sign-in and, because sign-in matched the
stored address, took their chosen address with it. The rewrite line is older than
this epic, but S3 made it reachable here by matching adoption across spellings. It
now runs only when the mailbox GENUINELY changed, and lives in a named helper rather
than inline, so the rule has one home.
The three lookups that resolve a typed address -- password login, password reset,
verify resend -- go through find_user_by_email: exact spelling first, then the unique
canonical candidate, and None when several accounts share a mailbox rather than
guessing which one a password should open. Reset and resend previously answered a
different spelling with silence (they reply uniformly by design), which was a dead end
with no way out. Their mail now goes to the address on the account, never the one
typed into the form.
peter
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