Just for anecdata: I'm using simplelogin to alias my emails and I can see there is a 20ish minute window between when Simplelogin receives an email, to when it finally shows up in my Proton inbox. Normally it's an inconsequential delay.

Not sure if that indicates how much of a backlog of emails Proton has because of this outage, or if the DR infra is just that much slower?