I have enabled the Cloudflare Email Routing beta for my domain once I learned the solution to 550 Domain does not exist error is to disable and re-enable catch all forwarding.
I noticed that when configuring DNS settings for Email Routing that Cloudflare suggests that I add this SPF entry into DNS:
TXT [my domain name] v=spf1 include:_spf.mx.cloudflare.net ~all Missing
If I’m not mistaken, this entry would only make sense if I was using cloudflare’s SMTP servers to send outgoing mail. But as far as I know Cloudflare doesn’t offer outgoing SMTP servers. Thus I am ignoring this suggestion and leaving the SPF entry to what my mail provider recommends. Perhaps there is a good reason for making this recommendation that isn’t obvious to me.