I must have gotten lucky because mine just works. My exact setup is mailinabox installed on a vps at vultr. Have been sending to gmail addresses mostly fine. Had 1 email go to spam in 2018 but everything else has gone through correctly.
Since mailinabox configures everything for you maybe the issue is that when you set it up yourself you don't quite get it exactly right to what gmail and microsoft demand.
Since mailinabox configures everything for you maybe the issue is that when you set it up yourself you don't quite get it exactly right to what gmail and microsoft demand.