We had some problems with this project as our domain name used one server and IP for processing emails and another for web server. We need to send emails using php from the web server for contact us purposes.
The SPF record is connected to the email processing server.
Don kept working with us for several weeks until fully understood problem. He did not charge extra and provided key info.
I give him 5 stars.
Fix php Mail Command Problem
on Oct 24, 2017