A problem has been discovered with cyrus-imapd 2.3.15 on Mandriva
2010 Spring, in handling the IMAP COMPRESS option.

Cyrus imapd 2.3.15 implements the IMAP COMPRESS option, in order
to compress data between the imap server and clients that support
this option, eg. Thunderbird 3. A problem has been discovered in the
implementation which causes the inability to upload large messages
to the imap server.