Re: [VM] Info node "External Messages"

[Uday Reddy]

Alan Wehmann writes:

> I can emphasize the following conclusions from this evidence:
> 
> 1) Thunderbird is synchronizing a file on my computer's hard drive,
> matching the contents of the IMAP inbox folder.

Yes, indeed, it does!  VM's IMAP folders work the same way too.  But what
shape the cache folders are in, before you force a full synchronization in
some way, are internal decisions for Thunderbird as well as VM.  They are
not meant to be portable across different mail tools.

(Note that Thunderbird also keeps essential information about the folder in
.msf files.  The format of those files is again internal to Thunderbird.  If
you make any changes to a Thunderbird folder inside VM, VM will delete the
.msf file.  For Local Folders, that is perfectly fine.  Thunderbird can
reconstruct the .msf file from the folder itself.  For IMAP cache folders,
deleting the .msf file can result in loss of information for Thunderbird.
So messing with Thunderbird's cache folders inside VM is not recommended.)

> 2) The setting of 50000 for "vm-imap-max-message-size" is working.
> Messages in excess of that size are having only their headers
> downloaded, when "vm-get-new-mail" is used.  The full message is
> downloaded if I choose it in the Summary buffer.

That is good.

> 3) It is possible to have VM parse the Thunderbird synchronization
> file (local on my hard drive), but it involves a bit of trickery.

Covered in my response to (1).

> My experience on April 4 (when I was using the IMAP inbox folder as a
> spool file), of being asked a) if I wanted to download each large file
> (answer no), and then being asked b) if I wanted to delete it from the
> "maildrop" (answer yes . . . bad choice, bad choice, bad choice) has
> me wondering about the design of those questions.  It seems to me
> rather odd to ask me if I want to delete a large message if I haven't
> even looked at it (with VM).

That was Kyle Jones's design.  I guess the idea must have been that, if you
don't want to download a message from the server due to its size, then it
would be sitting on the server for ever and ever, filling up disk space.
So, there must be a way to get rid of it.  Looking through the CHANGES file,
this has been there probably since VM 6.14 (February 1997), first for POP
then adapted to IMAP (July 1998).  In those days, mail servers were meant
for delivering email, and you were expected to download the email as quickly
as possible and delete it from the server.  So, it made sense.

POP folders were implemented in December 2001.  "External messages" (headers
downloading) was planned but never done.  Here is a thread on vm.info
archives which indicates the plan:

https://groups.google.com/forum/?fromgroups#!searchin/gnu.emacs.vm.info/pop$20max$20message$20size/gnu.emacs.vm.info/17qDHuWoIqc/HiuVa_FoIfgJ

(Look for Terry W.'s message on 2/21/2002 and Kyle's responses.)

Now that we have external messages implemented, that is the preferred way of
reading IMAP mail.  We should regard the idea of IMAP spool files as a
historical relic that is out-of-date and to be avoided at all costs.

Cheers,
Uday