Reproducible as follows: 0) Reboot the device 1) start kmail-mobile 2) Write a mail and touch "send" 3) Deny Kwallet access 4) Deny to enter imap password 5) An "email successfully sent" message will appear, although the email is in outbox. Observed in version 4:4.5~20100930.1181090-1maemo1.1180919_093920.
The actual text is "E-Mail successfully sent".
Fixed in revision 1200753.
I can verify that the email successfully sent notification after volkers fix only shows up when a mail is successfully sent. Although only tested on WinCE the problem was the same.