It is possible to choose "Write new Mail" and touching "Send" immediately. There is a lack of feedback when trying to send a message 1. to no recipient 2. without subject, 3. without content. (Version 4:4.5~20100813.1163254-1maemo1.1164259)
Commit 1164473 [1] added a warning for empty subject and/or recipients. Empty content still not checked verified. [1] http://websvn.kde.org/?view=revision&revision=1164473
I can't reproduce this bug on Linux. When clicking on 'Send' a 'No recipient found - Kmail Mobile' pop up message appears saying:'You should specify at least one recipient for this message'. Please retest and verify if it does not happen anymore. N900, 4:4.5~20100901.1170574-1maemo1.1170522
Confirmed for 4:4.5~20100827.1168757-1maemo1.1169941 , too.