I am running into 2 issues with new email notifications on OS X. For now I'm reporting them here together, if either one should be reported against another KDE component I'll be happy to create a new ticket.

In short:
1) message popup notifications steal focus on OS X, and don't return it.
2) I cannot seem to deactivate the popup messages. This one is actually new since yesterday - but I haven't code nor settings files.

Reproducible: Always

Steps to Reproduce:
1. Start kmail
2. Bring some other application to the foreground, interact with it
3. When new mail arrives, a message pops up, grabbing the focus and not returning it.
4. Check if you want pop up notifications in the 1st place

Actual Results:  
Pop up messages grab focus and don't return it to whomever it had.
According to the notifications settings, they shouldn't appear in the 1st place.

Expected Results:  
1. Pop up messages don't grab focus and even if they did, they'd return it to the previous owner.
2. Pop up messages appear only for events for which they have been configured.

Re. 1) in the expected results: OS X provides the means for this. The resulting messages might be less "rich" as pure KDE ones (no theming for starters) but at least they "behave"

OS X is going to be restricted to running KDE 4 applications for a while longer, and MacPorts is only now preparing the move to 4.13 . Hence the report against "such an old" kmail version.

I'd be happy to have a look at how these popup messages could be improved on OS X (possibly even "backporting" the approach used in KF5, if relevant) but I'd need some pointers about where and for what to look, etc.