Sync'ing "Sent"-box between Mail.app and e-mail sent using the web-app (2)

Question

Hi,
A while ago, I posted this question, and Allan Sampson provided the answer, how to do it quickly and efficiently (see below).
However, that method turns out to have a flaw:
Here's what I just posted to Apple's sofware feedback:
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During the week, I connect to the internet from behind a firewall that prevents IMAP usage. I therefore use the webmail access to my @mac.com account. Once I am connected from a more liberal network, I let Mail.app sync with the @mac.com account, and transfer the "sent" messages from the server (the "Sent Messages" sub-folder at the bottom of the left-hand side folder listing in Mail.app) into the "Sent" (paper glider looking) folder, to be stored locally. I store about 7 year's worth of e-mail and use it as database.
Unfortunately, when so transfering the sent messages from the @mac.com server into the local "Sent" folder, the "Date Sent" inexplicably changes to the date of transfer, and the original date of sending is obliterated!!! This should not happen, and I cannot but consider it a bug in Mail.app.
Please fix this ASAP!
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In the meanwhile, does anyone know of a workaroud, other than forwarding those "sent" messages to myself, whereby the original header with the original "date sent" would be retained?
Thanks, Tristan

Answer 1

Tristan, we’re getting nowhere. For some reason that escapes me, you keep ignoring, misreading and/or misunderstanding what I’m saying...
At this point, I can only guess that you don’t really know what I’m referring to when I talk about message headers. The message headers are not the same as the column headers that Mail displays in the message list. The message headers is what Mail shows above the message body when viewing a message. You can choose the amount of header information that Mail shows there by default in Preferences > Viewing > Show header detail, and you can tell Mail to show all the headers while viewing a message by doing View > Message > Long Headers.
There is no such thing as Date Sent or Date Received message headers. The date & time that Mail shows in the Date Sent column is the date & time that appears in the Date message header and is set by the sender’s mail client. The date & time that Mail shows in the Date Received column is the date & time that appears in the latest (topmost) Received message header and is set by the recipient’s incoming mail server.
If the message headers that Mail uses to determine the date & time that it should display in the Date Sent and Date Received columns are missing, Mail cannot reliably show the right date & time there, but it may still try to do so by looking somewhere else, such as the Internal Date message attribute if the message is stored on an IMAP server. Problem is, contrary to what happens with the message headers I’ve mentioned, the Internal Date is an IMAP attribute that isn’t part of the message itself, and hence, is lost as soon as the message is moved out of the server...
Before the transfer:
<http://homepage.mac.com/thubsch/eMailTransfer0.gif>
What you’re showing here is Date Received, not Date Sent, but I could say the same I’ve said about Date Sent in previous posts, except in this case Mail gets the date & time to be displayed there from the latest (topmost) Received message header. The thing is, that header is set by the recipient’s incoming mail server, so don’t be surprised if you don’t see it either by doing View > Message > Long Headers while viewing a sent message...
Again, if that message header is not present, Mail will have to get the date & time to be displayed in the Date Received column from somewhere else. In particular, if the message is stored on an IMAP server, as is the case here, it can determine that date & time by querying the IMAP server for the Internal Date message attribute, just like it can for the Date Sent column when there is no Date message header.
BTW, note that Date Received is meaningless for sent messages (Mail has absolutely no idea when the messages were received, not even whether they were actually received), but since those messages would normally have no Received message header, Mail would actually display the right sent date & time in Date Received for sent messages if the Date message header was present.
However, I wish to store those messages on my machine locally. In answer
to my earlier question (for which you cited the URL), the really simple
procedure was recommended, to select all messages from "SentMessages"
and press-and-drag them into the "Sent" folder. When I do that, the "Date
Sent" for all those messages becomes the date & time of transfer:
<http://homepage.mac.com/thubsch/eMailTransfer1.gif>
And again, when you do that, Mail can no longer query the IMAP server for the Internal Date message attribute. Since the message headers that you keep ignoring and that Mail needs in order to be able to show the right date & time in the Date Sent and Date Received columns aren’t there either, Mail simply has absolutely no way of knowing what date & time should it display there other than by looking at the creation date of the *.emlx files associated with those messages...
Now, you are welcome to write a dissertation on how come this happens and
why this is not a bug in "Mail.app". However, you are missing the boat:
Interestingly enough, I’ve already explained multiple times why that happens and why this is not Mail’s fault. The culprit here is the mail client used to send those messages, which fails to set the Date message header that Mail (or any other mail client, for that matter) needs in order to be able to determine what the Date Sent is supposed to be.
It’s you who keeps missing the boat and ignoring, misreading and/or misunderstanding everything I’m saying...