When moving multiple message from the Inbox (other folders as well?) to another folder, the messages are moved but stay displayed in the Inbox. This does not happen when moving individual messages. The KMail version info is: Version : 17.04.1 Release : 3.fc26 Architecture: x86_64 Install Date: Thu 13 Jul 2017 09:41:42 AEST Source RPM : kmail-17.04.1-3.fc26.src.rpm
Sounds exactly like bug#380182, which should be fixed in 17.04.3 and later. Maybe ask your distribution to update the packages or backport https://cgit.kde.org/akonadi.git/commit/?id=2dc7fbf569ba3f7eeef98fb818d7af0820caf7a3 *** This bug has been marked as a duplicate of bug 380182 ***