Issue with Maximum Message Length

[Kingfish]

Hi I am a new user and I am experiencing some issues with the Maximum Message Length. When I went to make my first Thread on my forum I realized I needed to change the default settings as I was hitting the Maximum Length and getting an error. I read through the forums here and found out I needed to change the Maximum Message Length under the configuration setting. I set it to 0 as that said there wouldn’t be any limit. I went back and tried to start the same thread and ran into the same problem it seems I get errors if I try and start a thread in excess of roughly 1,200 words and changing the settings via posts configuration doesn’t seem to change anything.

The error I get whenever I exceed roughly 1,200 words is:
Forbidden

You don't have permission to access /newthread.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

[Yumi]

This doesn't look like it's related to a MyBB setting.
Can you make new threads if you have less text?

[Kingfish]

Yes, I was starting to come to the same conclusion so I sent in a ticket to my host they said a mod_security rule was getting flagged they quickly resolved it.

This doesn't look like it's related to a MyBB setting.
Can you make new threads if you have less text?