Yeah I mean a lot of people are nonchalant about it here, but email for business is like telephones. Basic infrastructure that has an assumed near-zero downtime and expectations of fault tolerance.

It's such bedrock infrastructure that I've seen it used as fallback in the event of electronic trading infrastructure outage, brokers would accept specifically formatted emails as orders.

At this point it would probably be less impact to have phones go out globally because people would fallback to walking across the floor, using zoom/slack for simultaneous communication or email for more async.