Asked a similar question a few years ago, ended up switching to Mailgun out of frustration. However, after a while I did get PHP mail to work with Postfix, however since then I have moved to a new domain, and all emai...
Been trying to get mail to send all day without being flagged as spam, but they still are.
My IP is not blacklisted.
Here is the source for one of my emails sent to gmail: