I have set up kmail for encryption and configured 'gpg'. When sending an email to a correspondent whose public key I have a window pops up and asks me whether I want to encrypt that email. When I request 'encryption' another window appears with the relevant encryption key and asks for confirmation. After I confirmed the email is send - it appears to me encrypted - but in fact is not encrypted. However, when I select the 'padlock' on the menu bar before clicking the 'send' button the email is in fact encrypted and send. I can't believe that the developer(s) intended that behaviour.
I may add that the item 'Automatically encrypt messages when possible' has been checked in the settings of kmail.

You may want to file a bug on bugs.kde.org. If possible, check first if the behavior occurs with 4.12 first.

Just received an update from kmail 4.11.3 to 4.11.4. The problem seems to be fixed now.