On a fresh install of 4:4.5~20100827.1168757-1maemo1.1169941 , write a mail and press send. As no account was specified, delivery will fail (with contradictory messages). The mail is however lost (neither found in outbox nor in sent-mail). The message should stay in the outbox until delivery succeeded or the option to send a mail with the (default) unknown identity should be disabled.
Should be related to https://bugs.kde.org/show_bug.cgi?id=249993
*** This bug has been marked as a duplicate of bug 249993 ***