[Dovecot] mailsync: NO Unexpected EOF

Hello,

I am trying to migrate off a MS Exchange 5.0 server. I am using mailsync (http://www.linux-france.org/prj/imapsync/) to copy the files to a Dovecot server, version 0.99.10.7. For particular messages I get the following error:

Couldn't append msg #114081 (Subject:[RE: balh blah]) to folder INBOX: Error trying to append: 826 NO Unexpected EOF

I think this is Dovecot, complaining about the message text that imapsync is trying to append/write. If this is Dovecot, is there any setting I can set to fix this?