4.14.6 (kmail-4.14.6-16.2.x86_64, current in openSUSE 13.2) but I believe the issue has been there before. Sending email through SMTP (TLS+authentication) reliably works while kmail still counts "1" email in the local outgoing mail folder ("Postausgang"). There's actually no mail left and all went fine, it's however indicated in the folder list and very misleading as it appears as if something went wrong. The "1" disappears when I click the (empty) folder. The error doesn't happen always but fairly often. I'll probably attach two screenshots. Please let me know if there's anything for me to try out to help fix this. Reproducible: Sometimes
Created attachment 91731 [details] wrong count for the outgoing mail folder Postausgang
Created attachment 91732 [details] count reset after clicking the folder
I confirm it.
This bug has never been confirmed for a KDE PIM version that is based on KDE Frameworks (5.x). Those versions differ significantly from the old 4.x series. Therefore, I plan to close it in around two or three months. In the meantime, it is set to WAITINGFORINFO to give reporters the oportunity to check if it is still valid. As soon as someone confirms it for a recent version (at least 5.1, ideally even more recent), I'll gladly reopen it. Please understand that we lack the manpower to triage bugs reported for versions almost two years beyond their end of life.
Just as announced in my last comment, I close this bug. If you encounter it again in a recent version (at least 5.1 aka 15.12; preferably much more recent), please open a new one unless it already exists. Thank you for all your input.