This is just a FYI for Tableau Server admins who have implemented VizAlerts.
I was getting an undeliverable email error once a week for a couple of weeks. No big deal, I figured it would go away once I processed the weekly terminations list I get from HR or when I deleted the Unlicensed users from the Tableau Server. Nope. Happened again this week so I knew there was something else going on.
While the person was a full-time employee, they were not registered on our Tableau Server, thus their email address was legit even though I couldn't "find them" on the Server.
At least you now know that if you can't figure out how an email is being sent and bouncing even though the person doesn't exist on the Server in the first place you can look to VizAlerts as a possible cause. Now, how you find the offending report and let the author know...
Thanks for sharing, Toby--good to know. My co-worker Geoff Nelson is interested in contributing some code to do tracking of VizAlerts operations. I've wanted that for forever, too. Maybe we'll get some traction on that, now!