Hi all
I am sitting with the same issue on the new VPS that I moved to.
On the shared server the normal email functions was fine most of the time, but on the VPS the "from" line use to read: myemail@mycompanydomain.coza
On the VPS it is the same exept it has the "cpanelname@servername.coza on behalf of Compny name <myemail@mycompanydomain.coza>
According to the hosting provider, the VPS does not have cloud linux installed, since it costs extra, where shred server have this isntalled, and thus the reason for the above problem.
I have now trying to install https://github.com/serbanconstantinescu/fa_mail_phpmailer and will see what it does.
I have been using PHPlist (Mailing list) for a long time and they have implemented and option to use the normal php's mail() function or you could change the smtp settings in the config file using phpmailer6 , maybe you could have a look at it.
My deliverability is better with the smtp function through my mail server.
Will see if the serban idea will work and report back