I don't know if it's that simple. As a litmus test, try to set up your own mail server. See how many milliseconds it takes for it to be blacklisted by gmail. And then observe the response time for their support, when you try to clear up the confusion that google has about your intentions.
I find there are three peopls who comment about hosting email. A small group like us who set it up correctly and never have problems. A larger group who set it up but get the dns wrong and warn people not to. And a third bigger group who never tried but listen to the second group and always comment that you'll have 1% deliverability
It was dead-nuts simple in the 1990s: Just learn enough about DNS to put in an MX record that points to an A record, get sendmail working, and have it begin delivering mail. The end. (Open relay? No spam filter? No virus scanning? No nothin'? Yeah, that kind of was the style at the time...)
It's got a lot more steps today, but it's still do-able. Operationally, keeping a mail server online and treated well just takes one or two people to spend a little bit of time occasionally to stay proactively ahead of new expectations and requirements instead of reacting to them after things change.
It also helps if Carla, from marketing, doesn't wake up one day and decide to spam the entire customer list without asking for guidance first. Maybe I should have put some automatic mitigation into place for that, but whatever: We chatted about that and it never happened again.
(Or at least, I find that to be true with smaller companies. Bigger ones obviously may require more elaborate systems to handle more volume and/or provide better uptime. But the requirements of keeping the reputation up are about the same regardless of scale, and that still only takes one or two people to pay attention to things sometimes. [And the only reason two might be required is in case one of them gets hit by a bus.])
"Blacklisted" probably doesn't have a sufficiently clear definition. I don't even run my own server, just use a custom family domain that is served by protonmail, and discovered when trying to go through foster licensing that virtually all of the agencies were not reading my e-mails because Microsoft and Google alike were routing them into the spam folder, but they weren't being blocked or bounced. I wouldn't have even known if I hadn't called a few and asked them to check.
I am definitely not being flagged for any actual spam-like behavior. I might send out 40 e-mails a year, and even though it's a "family" domain, I'm the only one who has ever used it, ironically enough, as part of my decade-old effort to de-Google.
I've built mail servers before Gmail existed that lasted long enough to get blacklisted by Gmail.
Fixing it was always pretty simple -- or at least, non-mysterious. They'd bounce some things, I'd look at the headers of the bounced messages, and therein were links to instructions there that showed how to resolve whatever issue it was this year.
Just follow the steps, implement the new thing, and stuff started flowing again in rather short order. Not so bad.
IIRC, the only time it ever cost us any money was when the RBLs started keeping track of dynamic IP pools and we needed to finally shift over to something actually-static.
