[Bug 1244369] [NEW] Keeps pausing for ages whilst downloading IMAP

[Derek]

Public bug reported:

Running 24.0.1 on Windows 7 x64 Ultimate.

I'm trying to download my brother's Hotmail e-mai for him, so that I can
then copy it to the Local folders as an offline backup. However, it's
taking ages because TB keeps pausing for ages and no apparent reason.

My brother has a number of folders for his e-mail on Hotmail and for
example, on the folder 2009 it stopped for several minutes at 144 out of
272. Then it get to 153 and paused again for several minutes, then it
went to 269 and paused again for several minutes. It's probably taken at
least 15 minutes so far just to do that one folder. When it got to 272
out of 272, it again paused for ages and then when it had finished, just
didn't do anything for a while. Now it's start on the folder "2010" and
has got to 14 out of 1420 and paused again. When it's paused, Task
Manager shows that TB is not doing anything.

Under Account Settings I have "Keep messages for this account on the
computer" and have all his folders except for Deleted ticked. However,
if I right-click on the Account in the main window and select Subscribe,
it shows all the folders, including Deleted, ticked so obviously these
settings are for different uses.

If I disable "Keep messages" and then drag each IMAP folder to Local
Folders to copy it, it doesn't seem to pause and although slow (no doubt
a limitation of IMAP) it steadily downloads the messages and Task
Manager shows around 2-3% CPU. However, if I drag multiple folders to
copy instead of a single one, it does seem to start pausing quite often
again, even though it's only copying one folder at a time, perhaps the
others being queued triggers the problem.  Actually, I just tried again
only dragging one of the folders "Newsletters", which was the first one
it was copying when dragging multiple folders and that's having
problems, currently paused at 41 out of 151. Several of the folders I'd
copied previous to this one had the same amount of e-mails and didn't
pause, so it doesn't appear to be the number of e-mails in a folder
that's the issue.

Testing on my own system the other day, with both Hotmail and Gmail
accounts, I found that when copying the mail from the IMAP folders to
the Local Folders, it appeared to be downloading it all again, despite
it already being stored on my PC, which doesn't seem right. It also
seemed to make no difference to the size of the TB data files when
disabling "Keep messages for this account on the computer" with Inbox
being around 600MB and Sent around 550MB.

** Affects: thunderbird (Ubuntu)
     Importance: Undecided
         Status: New

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Title:
  Keeps pausing for ages whilst downloading IMAP

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