Ah, yes, forgot to mention that as well. I had the same problem with
Sierra turning on UI sound effects, and I quickly turned them off. Not
sure why, but I had also set the volume slide for "blow" to zero (and
that one keeps going in Mailmate), whereas I hadn't done that to "glass"
(which had
FWIW I was running with all alert sounds switched off in System
Preferences, and the upgrade to Sierra switched them back on.
To restore my pre-upgrade settings, System Preferences -> Sound -> Sound
Effects, then
* move the Alert volume slider completely to the left
* uncheck "Play user
With the update to "macOS" Sierra, Mailmate (v 1.9.5 - 5263 and
then 5268) has started giving sound notifications -- first "glass" and
then "blow," I think. I've turned them off in two places:
* System Prefs > Notifications > Mailmate (alert style - none, and all
checkboxes unchecked), and