> According to the support, the notification emails to the users were sent on Feb 23, Apr 6 and May 15th. However, we did not receive those at all. If true, this is concerning. One message getting lost in spam understandable. But three over 6 months would imply they're being blacklisted and/or their mail sender is simply broken. Do serious companies not have canaries or other checks in place to ensure their notificat…
Even with a canary, you have no guarantee that a particular customer will receive your email. In this case, maximum CYA is a certified letter sent return receipt requested. There are services out there to mass mail those.