I can't unselect the SSL box

I'm having trouble sending emails. It's giving me a rejected by the server error so I select the Edit SMTP server list button and under the advanced option the "Use Secure Sockets Layer (SSL)" box is checked and according to my server support that button is suppose to be unchecked. Everytime I try and uncheck the box it just stays checked.

Do I have to uninstall the account and reset it up?