Comment 13 for bug 220991

My outgoing SMPT server was MS Exchange, but I don't think that it is root of the problem, because of later I can download valid attachment through web-interface.

I'm not sure IMAP server is MS Exchange, perharps not. I don't know how to determine it. For testing I used my own account on the free e-mail service http://www.mail.ru and its IMAP service is imap.mail.ru

In bug 384819 the source of problem was interruption of message downloading, but I didn't it. Reindexing or clearing cache helped in that bug, in my case it doesn't.

I think it is not DUP, but more likely extension.

Below is sample message source (Ctrl+U), if it may help someway:

From <email address hidden> Sat Aug 04 12:54:59 2007
Return-path: <email address hidden>
Received: from [213.128.220.224] (port=30189 helo=[213.128.220.224])
 by mx5.mail.ru with asmtp
 id 1IHFOM-0000YO-00
 for <email address hidden>; Sat, 04 Aug 2007 12:53:47 +0400
Message-ID: <email address hidden>
Date: Sat, 04 Aug 2007 13:53:40 +0500
From: Ivan Kadomin <email address hidden>
User-Agent: Thunderbird 2.0.0.6 (Windows/20070728)
MIME-Version: 1.0
To: <email address hidden>
Subject: test
Content-Type: multipart/mixed;
 boundary="------------060200080805050905070205"

This is a multi-part message in MIME format.
--------------060200080805050905070205
Content-Type: text/plain; charset=KOI8-R; format=flowed
Content-Transfer-Encoding: 7bit

body text

--------------060200080805050905070205
Content-Type: application/pdf;
 name="2 =?KOI8-R?Q?=E9=EE=E6=EF=F2=ED-=F0=E9=F3=F8=ED=EF-=D2=D5=D3-02-05-2007=2E?==?KOI8-R?Q?pdf?="
Content-Disposition: inline;
 filename*0*=KOI8-R''%32%20%E9%EE%E6%EF%F2%ED%2D%F0%E9%F3%F8%ED%EF%2D%D2%D5;
 filename*1*=%D3%2D%30%32%2D%30%35%2D%32%30%30%37%2E%70%64%66
Content-Transfer-Encoding: base64

JVBERi0xLjQNJeLjz9MNCjExNSAwIG9iaiA8PC9MaW5lYXJpemVkIDEvTCAxODk4ODgvTyAxMTcv
RSAxNzk4ODUvTiAxL1QgMTg3NTQwL0ggWyAxODEwIDMxM10+Pg1lbmRvYmoNICAgICAgICAgICAg

.......... I truncated a number of base64 lines except last two, ...........
.......... there are nothing more in message source after them. ...........

MDQnMDAnKS9fQWRIb2NSZXZpZXdDeWNsZUlEKC0xNTU1MjQ3MzQ3KS9Db21wYW55KP7/BBwEEwQi
BCMpL1NvdXJjZU1vZGlmaWVkKEQ6MjAwNzA1MDMxMjM0NDApL1RpdGxlKP7/BB

I attached 185 Kb PDF, when I did "Save As..." it became 183 Kb. It looks like not all base64 lines are present and there is no usual ending line, such as:
--------------060200080805050905070205--