Andrew Gierth wrote:
"Dave" == Dave Crocker <dcrocker(_at_)brandenburg(_dot_)com> writes:
AG> Mail systems do not appear to make any actual use of the
AG> message-id header other than for logging (and internally in some
AG> odd systems). None of SMTP, POP3 or IMAP ever use message-ids as
AG> protocol parameters.
Dave> Message-ids are not nearly as deeply and usefully and broadly
Dave> used as we had expected them to be. However, they ARE used, to
Dave> good effect, for duplicate detection and for thread
Dave> construction.
at the layer of actual message transport, or just in the clients or
client-side services such as IMAP threading? I really wasn't referring
to the clients when I mentioned "mail systems".
I have heard of mail transports that assume a 1-1 correspondence
between message-ids and body content but I believe this to be highly
unusual; please correct me if I am mistaken on this point.
FYI, the LMTP daemon in Cyrus IMAP uses the message-id for duplicate
suppression (and to prevent mail loops) at the time of delivery. This
isn't done as part of the protocol as in NNTP, but its done internally
for every message before its committed to disk.