That's really not true though. That's what the cloud companies told us.

We've had more downtime from all our SaaS and cloud services in the last year than the 20 years before when self hosting.

When we self hosted, we very rarely had an unplanned outage. It really shouldn’t happen all the time. Plus I could work planned outages around the company’s schedule.

Now it feels like something is always down.

That's all predicated on having a team of people with the appropriate knowledge of how to securely self host an email system. Some organisations aren't big enough for that to be worthwhile, others have decided to forego that cost to let the cloud providers pick it up.

Email is not a particularly easy thing to reliably host and secure for a sizable organisation, especially if its not your main focus.