Local parts are ASCII-folded — never str.lower(), which maps U+212A onto "k"
and would resolve a look-alike to someone else's mailbox — for everything we
own or resolve: mailbox lookup, login identity, inbound recipients. Domains
are IDNA-canonicalized. Addresses we merely carry, in contacts and MIME
headers, keep the case they were typed or received in. core.mda.addresses is
the single policy, held in place by a pylint checker and an eslint rule that
ban hand-rolled '@' splits and Unicode case folding.
Migration 0035 folds existing rows and reports the collisions it will not
merge on its own. Also drops mta-out, and adds dual RSA+ECDSA certificates,
per-refusal logging and an mta_session correlation claim to mta-in.
Notably, we try to reduce disk usage by standardizind on common
base Docker images. We also improve node_modules by reducing
duplicate dependencies and install speed.
