Inconsistent handling of MHTML attachments

The Real Doctor (for it is he) wrote:

I use Thunderbird under Ubuntu 10.04 as an IMAP client for the Exchange
server as work. Every so often I get email message with important MHTML
(.mht) files attached.

When I retrieve these messages on my desktop machine, or on one laptop,
the files are sized at 0 bytes.

Does Tools > Activity Manager show anything relevant? Note that these
entries aren't in date order IME so you may have to hunt around.

Another thing, there's a max size parameter for IMAP messages. I find that
Thunderbird doesn't say anything obvious about the size when trying to
retrieve messages larger than this, it just seems to sit there like it's
trying to download it, but never does.

If you're getting desperate you could try IMAP in plaintext mode [if
allowed] and packet capture it.

Is this inconsistency something at the Thunderbird end - ie something I
can sort with a config change - or is it more likely to be at the server
end? As far as I know the various Thunderbirds are set up the same, and
no other attachments are affected.

You could copy the profile from the working to non-working client and see if
that fixes it.

When I use Outlook Web Access the MHTML files are shown as "blocked by
OWA"

Well that sounds like a clue, but why would it allow some clients but not
others? Exchange brings with it a phalanx of WTFs IME so who knows...

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