Then you should have a reputable IP that can be used. Otherwise you're probably screwed because residential IPs are nearly impossible to get off the lists.
That's how I'm doing it right now. I have my Fastmail as a backup but I've been migrating nearly all my email usage to self-hosted. The Fastmail is my insurance plan if I get hit by a bus so my wife can keep accessing the really important stuff, do password resets, etc. A bad power outage or crash and she'd be screwed because my homelab stuff is all full disk encrypted...