Confira as " mensagens de resumo da sequência " applescript. Da sua descrição:
This AppleScript for Mail will take one or more selected digest messages (messages formatted as either multipart/digest (MIME digest) according to RFC2046 or simple digest as defined by RFC1153) and extract the individual messages from the digest message - this is especially useful if you are subscribed to a mailing list in digest format but want to reply to a single message in the digest rather than the digest message itself.
(achei isso na lista de plug-ins do Mail do HawkWings.net )