The OpenConnectionTask::handleStateHelper function in Imap/Tasks/OpenConnectionTask.cpp in Trojita before 0.4.1 allows man-in-the-middle attackers to trigger use of cleartext for saving a message into a (1) sent or (2) draft folder via a PREAUTH response that prevents later use of the STARTTLS command.
https://github.com/jktjkt/trojita/commit/25fffa3e25cbad85bbca804193ad336b090a9ce1
http://jkt.flaska.net/blog/Trojita_0_4_1__a_security_update_for_CVE_2014_2567.html