need to change the default "Automatically update e-,ail addresses based on recipient policy" to unticked

Hi

we had an issue, where by we had to add another domain to our exchange server to the recipients policies default policy, which worked okay, we have 5 other domains in this list also as our company is split into sub company names, so users have different email addresses i.e. jobloggs@company1.com billbloggs@company2.com .. one thing that was done differently this time when adding this new @company5.com domain was to right click "Default Policy" and select "Apply this policy now..." which changed all of the 250 users primary email address to the same by which we think was applying the tick in "Automatically update e-mail addresses based on recipient policy" but to add even more mistery is for the x years of adding new users to the system we were able to alter their primary email address to something different to what is set on the recipient policy in exchange and not have to un-tick the "automatically ....." option which is ticked by default, so my question is how are we able to alter the default setting maybe using ADSI edit  to alter the default to unticked?? as this worked before.

Thanks guys

Jim