I have used a custom domain for longer than a decade. I've so rarely had an issue with deliverability that I can't recall a specific instance of it right now. J

I have used a custom domain for longer than a decade. I've so rarely had an issue with deliverability that I can't recall a specific instance of it right now. Just set up all the required dark magick like SPF and DMARC and use a quality backend provider. I've used multiple backend providers for it. FastMail for the majority of the time, though I switched off about 2 years ago. It worked great and I recommend it. Before that I used Google Apps (or whatever they call it now). I would not recommend using a custom domain with Google Apps. They routinely block you from using things that regular Gmail accounts can use, and I don't trust Google not to discontinue any given service. I briefly tried running it myself, and it wasn't worth the pain.