Version: (using KDE 4.4.1) Installed from: Fedora RPMs When an email with Disposition-Notification-To header is opened for the first time, the user is asked whether to send ack, nack or ignore. There is no way to postpone the decision - once user selects ignoring the Disposition-Notification, no chance to send ack later. I've tried to mark the email as new/unread, but it did not help, I never got the question again. And I haven't found any menu item to send the notification explicitly.
Thank you for taking the time to file a bug report. KMail2 was released in 2011, and the entire code base went through significant changes. We are currently in the process of porting to Qt5 and KF5. It is unlikely that these bugs are still valid in KMail2. We welcome you to try out KMail 2 with the KDE 4.14 release and give your feedback.