InsightIQ stopped sending emails

I had been getting these nice reports (I can still access reports from the web-based console, so InsightIQ is able to collect data) by email.

But a couple of weeks ago, the emails stopped coming.

I went to Settings > Email, and cannot even successfully send a test email.

I have an internal email relay that is set to allow the InsightIQ's IP address, and it has in fact worked before.  The relay server's logs don't show any connections from InsightIQ's IP address.  The relay server and InsightIQ can both ping each other by name and IP address.

Has anyone seen anything like this, or have a suggestion what to check?  I have even restarted InsightIQ to no avail.

(InsightIQ vversion: 4.1.2.7)