I signed up with them ensuring I read their privacy policy. Based on my personal privacy threat model, I’m okay with their policy. This wouldn’t fit a more intensive threat model.

I haven’t read it recently but last I remember they do have the option to temporarily store an email in the event of a failed delivery, until it can eventually get sent to you. This is opt-in I believe, and a toggle you can enable in your account.

In the time I’ve used them I haven’t had any issues with email deliveries. Been happy with the service so far, having left SimpleLogin and Proton for political reasons.