by bobw » Aug 27th, '14, 22:46
Yes. That was the case. There was an extra system tray widget in ~/.kde4/share/config/plasma-desktop-appletsrc. It's configuration section was deleted. However other pieces of it remained in the file. I wonder if it didn't get removed properly with the addition and removal of panel widgets?...
Anyway, I deleted all sections related to it, removed the current system tray, sent myslef an email (using 'mail' - kmail nicely informs me of system mail via the mbox account), noticed no popups, then added the system tray back, sent myself an email, and now got the single popup from notifier. All is well. Thanks for the help.