wp-includes/class-phpmailer.php problem

my wordpress installation is not sending e-mails. I tried to override mail function in couple ways: using wp-smtp-email plugin, adding actions to functions.php, sending through smpt – nothing works. the plugin log indicates that for some reason the code within wp-includes/class-phpmailer.php variables are not overwritten when sending messages. The messages are forced from “root@localhost” email which is clearly incorrect. The same website installed on similar but other hosting works flawlessly.

I tried to match server permission but they are the same 644. I even temporarily gave class-phpmailer.php full permissions to no avail. This is becoming increasingly frustrating and I can’t find no clues or solution. Any ideas? Thanks in advance.
Greg