Due to the newness of the domain combined with the heavy load from notifications and signups of over 1,000 accounts, the email had been blocked by our mail provider. Reasonably so.
Mastodon lacks the operator controls that a reasonable server would have (for me to force mail off for everyone), so your assistance in turning off email notifications would be greatly appreciated.
And hats off to Jarland and @mxroute, our mail provider (as well as poa.st's). Excellent service and very reasonable. 🙏