If a mail client Mozilla Thunderbird version 1.5 or above is installed and you use a Kaspersky Lab productto scan mail then configure the mail client for the Mail Anti-Virus component to function normally. You can do it the following way:
open Mozilla Thunderbird
in the menu select Tools > Options
go to the Advanced tab
click the Config Editor button on the General tab
in the open window in the Filter field enter CHUNK
right-click the filter mail.server.default.fetch_by_chunks
in the context menu choose Toggle
make sure the Value field has changed from True to False
right-click the filter mail.imap.chunk_add
in the context menu select Change
change the value to "0"
close all windows and save the changes
Note! By default the filter is enabled in the mail client. This filter allows receiving a message via IMAP protocol in parts. For normal functioning of the Mail Anti-Virus component a message should be received as a whole but not in parts. It is recommended to follow the instructions from this article.