It follows that if you just started using Fastmail, and there have been two nontrivial service outages in the past few weeks, that probably doesn't look very good.

On the other hand, I've been using Fastmail for years, and on the whole it has been very reliable.

And, at least on my end, the outage appears to be over now. :-)

You might consider giving Fastmail some more time before ditching it, but perhaps your email reliability requirements are more intense than my own.