GMail threading, IMAP and Ruby

Question

I am using the Ruby IMAP library to get a GMail conversation. The way that GMail threads conversations is via "Message-ID" and "In-Reply-To" message headers. For example:

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In-Reply-To: <c0f07c940909151905w1ad93fabx19cf595f653c8b@mail.gmail.com>
Message-ID: <9cd2f5ff0909151911r30ddb805n5172970dffc872c2@mail.gmail.com>

I cannot figure out how to efficiently get the replied-to message. The current way:

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target = <c0f07c940909151905w1ad93fabx19cf595f653c8b@mail.gmail.com>
imap.search(["NOT", "DELETED"]).each do |msg_id|
  uid = imap.fetch(message_id, "ENVELOPE")[0].attr["ENVELOPE"].message_id
  if uid == target
    m = imap.fetch(msg_id, "RFC822")[0].attr["RFC822"]
  end
end

It takes a really long time to do it sequentially like that, but I can't figure out the correct incantation to search by the Message-ID header, and I can't really find any evidence as to whether this is possible or not.

Answer 1

Apparently, the correct way to do this is:

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imap.search ["HEADER", "MESSAGE-ID", target]