The sad reality is, I'm thinking of moving my e-mail back to someone else. It might be Fastmail, might be Amazon. Running my own e-mail server is a pain and I hate having to send people a message on Facebook or Reddit saying, "I sent you an e-mail. Check your spam folder."
If I route my e-mail through Gmail's SMTP server as a relay, that shouldn't affect my DKIM/SPF stuff right? I'd just have to change SPF/DMARC to say gmail is allowed to relay messages for me, correct?
They do enjoy one big advantage over google besides privacy: tech support! Like a human, that reads and responds to issues submitted through their site! I've contacted them twice with questions about setting up my domain and one other thing and I got replies, from someone who knew what she/he was doing, within an hour each time!
Also, they will do a catch-all address (eg firstname.lastname@example.org) which receives email from every address not specifically defined. Thus you can implement the best anti-spam technique: every email you give out is email@example.com which forwards to firstname.lastname@example.org so you can tell exactly who sold or leaked your email address. eg email@example.com was sold all over the place.
I find it hard to believe that you get classified as spam for no good reason, unless perhaps that Linode / Digital Ocean are known for hosting so much garbage and people can be tempted to outright block them, but I doubt Gmail does that?