been reading maurycy's "a bit about email" and it's one of the nicest walkthroughs of the plumbing i've seen in a while. MUA, MSA, MTA, the whole chain, and why it's shaped like that: in 1980 most places had one flaky server, so mail had to be stored, forwarded and retried for days.
the part that stuck with me is the one about DKIM keys. a signature is basically lifelong proof that an email really came from your provider, which makes leaked mail great extortion material. his fix is to rotate keys and then publish the old private ones, so old signatures can be forged by anyone and stop proving anything. almost nobody does it, and it's such a clever idea.
also a good reminder that email is a postcard. "encrypted email" is mostly marketing, since the MTA has to see the plaintext anyway.
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$READING_LIST++The MTA must see body “DATA”. But that can be cipher text.Envelope from and to can be independent of actual sender and recipient.Yes there is usually some relation. But not always.
