Quote:
Originally Posted by PON
Same message sent to a distribution list
one person replies
duplicates are consolidated
one of the dupes has a reply symbol, showing the message was answered
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It would be interesting to confirm (i) that the message id is the same; and (ii) that the only difference is in the message headers. I think such a case, while unusual, is permissible. The behavior for duplicate suppression and dupe elimination would be up to the mail program. I think most programs doing duplicate suppression would suppress the later copy, assuming it to be different in the headers because of a different delivery route.
If the mailer wishes to transmit a slightly different message (such as an extra header that indicates the message has been replied to), I think a new message id should be assigned. If the receiving mail program is aware that mailers sometimes do not do this, a decision has to be made at the receiving end as to whether to include special case logic to deal with the erroneous behavior or delete the new version anyway.
It is possible that Fastmail and Thunderbird have made different decisions.