Error sending email to Could not execute: /usr/sbin/sendmail

I am not able to send a campainge. Process Q freezes up phplist to the point I can’t change screens, logout, stop processing, etc. When I do manage to log out and log back in, when I view the que the campainge seems to be running, but all emails fail.

I was getting the error message “could not instantiate mail function” until I edited line 127 in admin/class.phplistmailer.php (following jerryrat’s comments 12.25.16). Still can’t send a campaign.

I’m about ready to roll back to the previous version. Any suggestions.