Mozilla and their variants (firebird, phonix ...) allow you to customize how imap fetchs mail from the client. Add the following four lines:
user_pref(" mail.imap.fetch_by_chunks" , false);
user_pref(" mail.imap.mime_parts_on_demand" , false);
user_pref(" mail.server.default.fetch_by_chunks" , false);
user_pref(" mail.server.default.mime_parts_on_demand" , false);
to the user.js located at:
" <drive>:\Documents and Settings\<user>\Application Data\<mozilla,thunderbird...>\Profiles\default\<*.slt>\user.js"
to prevent mozilla from downloading imap emails in chunks.
An extension that can be installed into mozilla products will allow you to edit the file easily. It can be found at the following link.
http://extensionroom.mozdev.org/more-info.php/chromedit
Install instructions for Thunderbird (Mozilla and Firebird just left click the link, should install itself)
- just right click the install link and save the file to your harddrive
- select tools->options
- select the extensions button (on the left)
- Click " Install new extension" button and load the downloaded file.
- restart mozilla, thunderbird ...
- then " Edit User files" appears under the Tools menu.
Lots of other great extensions there too. 
