Mac Forum / Applications / Eudora / July 2008

This is really more a server-side issue, and is dependent on the server
being used and on the protocol: IMAP can actually be quite annoying in
this regard because UID's are really a hierarchical triple of the
mailbox, UID-validity-timestamp, and a UID number. As a result, you
cannot move a message between IMAP folders and preserve its logical
identity without tracking it on the client side in ways that are
intrinsically flawed. Conversely, the one-mailbox model of POP means
that its UID's almost never have any reason to be changed, so most POP
servers don't have any logic for making that happen.

So while the direct answer to your question is that the server UID for a
message is mapped to the Eudora copy of the message in the resource fork
of the mailbox that the message is in, there is probably some better
approach that actually causes the server to assign a new UID instead of
getting Eudora to forget that it has seen a message. If you really want
Eudora to forget that mapping (and all metadata about a message that
isn't in the actual data) for a POP-delivered message you can close the
file in Eudora, remove the resource fork, and change the modtime on the
data fork, and make sure you have Eudora's duplicate elimination turned
off (in the "Really Miscellaneous" setting pane.) I don't think
relaunching Eudora is necessary, but it could be. You might be able to
be less destructive to an entire mailbox by editing out the part of TOCF
#1001 (and 1002 if it exists) in the mailbox resource fork that refers
to the message in question, but that would be a very advanced technique
(sub-task #1: reverse-engineer the meaning of the TOCF structure...) For
an IMAP-delivered message, you can also manually tell Eudora to "Remove
Cached Contents" with the menu hiding under the server  status column
and you MIGHT be able to use AppleScript to tell Eudora to flip the
"will be fetched" property of a message to force re-fetching. I have not
tested that...

The better way to deal with this would probably be to change your
requirement from "get Eudora to re-fetch the same message repeatedly" to
"make the server present a copy of a message with a new UID" if that is
possible.

Exactly; that's what UIDs (server-assigned unique IDs for every message)
are for, so that POP clients can avoid repeatedly downloading messages
which the user instructs them not to order the server to delete,
by storing all the current UIDs
and comparing them to the set presented by the server next time;
the user typically chooses such a "leave mail on server" (LMOS)
setting either to share mail between multiple clients,
or to allow re-fetching recent mail if a client computer fails,
or to share access with a "webmail" viewer.

Indeed it must be, but Eudora doesn't document where for Mac
(it's in distinct files named "lmos.dat" under Windows).

Can you back up an "initial" Eudora Folder with settings already made,
and just keep restoring that entire backup folder, to in effect start anew,
without having to re-define any settings?

If you want to find out exactly where those UIDs are,
you could capture some UID samples either by manually logging in
with a "telnet" client and viewing the results of a UIDL command,
or by using some other email client whose UIDs are more easily found,
then search all Eudora files for matching strings;
after all, they do have to be somewhere,
and it would hardly make any sense to encrypt or disguise them
in any way that a tool for finding files containing a string can't find.

In addition, the modification time stamps on files can narrow the search
to those which are modified upon fetching new messages
or deleting old messages from the server, when LMOS is in effect.

--

I don't know where the UID's are stored, but one way to get all the mail
still on server is to check mail special, then click on "fetch all
message headers to Inbox."