Using the dolphin service menu to send file as attachment doesn't work if kmail is not running. Tried running 'kmail --attach <filename>' from the terminal throws a segfault if kmail isn't running.
Sending an attachment via the context menu -> Share... -> Send via Email does work for me, even if KMail isn't running. I suspect this might have been an issue with KMail. Please reopen this issue if you still have this problem with a newer version of Dolphin. SYSTEM INFORMATION Operating System: KDE neon Testing Edition KDE Plasma Version: 5.15.80 KDE Frameworks Version: 5.58.0 Qt Version: 5.12.0 Kernel Version: 4.18.0-17-generic