"From " -> ">From " in imap mail-source avoidable?

[Helmut Waitzmann <Helmut.Waitzmann@web.de>]

I sent two messages to me, each of them contained a line
beginning with the word "From".

The first message I read with the nnimap-backend, and everything
was fine.

Then I respooled it into the nnml-archive ('M-x
gnus-summary-respool-article') and everthing was fine again:


   From: Helmut Waitzmann <Helmut.Waitzmann@web.de>
   Subject: "From" am Anfang einer Zeile kritisch?
   To: Helmut Waitzmann <Helmut.Waitzmann@web.de>
   Date: 16 Jul 2002 19:15:41 +0200
   Xref: meine.maschine.example.com mail.private.misc:208
   Return-Path: <Helmut.Waitzmann@web.de>
   X-Sieve: cmu-sieve 2.0
   Return-path: <Helmut.Waitzmann@web.de>
   Envelope-to: MeineZweiteEmailAdresse@example.com
   User-Agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/21.2
   MIME-Version: 1.0
   Content-Type: text/plain; charset=iso-8859-1
   Content-Transfer-Encoding: quoted-printable

   Was geschieht mit folgender Zeile, wenn ich die Nachricht mit dem
   nnimap-Backend lese und mittels M-x gnus-summary-respool-article
   anschließend ins nnml-backend transportiere?

   From mir

The second message was grabbed by the imap mail-source specifier
from the imap server

   (list
    'imap
    ':server "mein.imap.server"
    ':mailbox "INBOX"
    ':predicate "UNDELETED"
    ':fetchflag "\\Deleted"
    ':dontexpunge nil
    )

and put into the nnml-archive:

   From: Helmut Waitzmann <Helmut.Waitzmann@web.de>
   X-From-Line: imap Tue Jul 16 19:20:34 2002
   Subject: "From" am Anfang einer Zeile kritisch?
   To: Helmut Waitzmann <Helmut.Waitzmann@web.de>
   Date: 16 Jul 2002 19:19:25 +0200
   Xref: meine.maschine.example.com mail.private.misc:209
   Return-Path: <Helmut.Waitzmann@web.de>
   X-Sieve: cmu-sieve 2.0
   Return-path: <Helmut.Waitzmann@web.de>
   Envelope-to: MeineZweiteEmailAdresse@example.com
   User-Agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/21.2
   X-Gnus-Mail-Source: imap:imap.example.com:INBOX
   MIME-Version: 1.0
   Content-Type: text/plain; charset=us-ascii

   Was geschieht mit folgender Zeile, wenn ich die Nachricht mit dem
   imap-mail-source ins nnml-Backend hole?

   >From mir

And as you can see, the last line has been mangled.  I guess,
that the mail fetching with mail-sources is the culprit:  nnimap
as well as nnml let the message intact, as can be seen from the
first message.  Is there a way to avoid this?  It looks like
mail-sources first puts all messages into a unix mailbox file.
But as I understand, that shouldn't be necessary, as can be seen
from the first example.