So I opened up the Mail.inc.php file and added a test email, it appears if I remove $headers then it goes through. It also goes through if I replace headers with a "From: firstname.lastname@example.org
\n" header. These are the headers it attempts to send:
Content-Type: text/plain; charset="utf-8"
X-Mailer: Open Journal Systems v2
Date: Tue, 26 Feb 2008 12:58:10 -0600
From: "our name" <email@example.com>