[otrs] Cannot switch off mx checking for emails

I first installed otrs with MX checking on, and got lots of messages about email addresses failing mx checks. So I reinstalled with mx checking off, but when I login as root and try and change the root email address it still claims the email address fails the mx check. 1) How can I stop these mx checks being done 2) could an option be added to the admin section to switch off mx checking after installation, to save re-installing. John