That's a 406 Error. Apache's Mod_Security spits it out whenever you do something it sees as a possible exploit of the server.
Are you sending via an SMTP server or through the PHP mail() function? Because I know that if you are running mod_security at high enough levels, Apache itself will prevent mass mailing via PHP.
Geuis Teses wrote:
I tried doing a mass email to 30-40 addresses.
Error when trying to send was from Apache:
Not Acceptable An appropriate representation of the requested resource / could not be found on this server.
Apache/1.3.34 Server at webmail.jtpre.com Port 80