We're using Collaboration in Connect.  Problem is that we don't get any emails from activity such as "Someone mentions me in a post or a comment." or "Someone comments on a post or a post I have commented on."

The in-app notifications appear OK.  The notification settings are all set up for "Instant" emails, but nothing is received.

Other emails are working OK, such as when someone notifies a process owner of a change to be reviewed.

So it looks like ARIS is set up correctly with our Exchange servers, but there's something about Collaboration in particular that's preventing emails from being sent.

Does anyone have a suggestion for what we might have missed?