Earlier quoted context omitted.
You really can't run your on email server nowadays though, you need to have been running one for several decades otherwise the email common email providers(gmail, outlook) will automatically just assume its spam. Also due to the way extensions added to the email protocol configuring and learning how to properly configure it so it gets accepted will be a dayjob.
This is a recurrent FUD dropping. I’ve run my own for about 15 years and it works. Occasional mails get sent to spam by Gmail, but that can happen if you use a big provider, too. Take an hour to set up DKIM, etc., and you should be OK.
In fact it'll happen even when you send from gmail to gmail itself!
My deliverability from my own email server to gmail feels better than from my company account (on gmail) to gmail users.