permissions in SendMail

I have set up Formmail which works fine to email addresses in the local domain. When the address is outside that, the message sends, but doesn't arrive. Log inspection lead me to believe that this is permissions related. (when the user is outside the local users list it can't authenticate?) Apple's answer for this (group writeable directory issue) is sudo chmod g-w / My questions are 1. Will this mess up other processes? (changing ownership at root level) 2. I heard Apple are moving to PostFix. Will PostFix work in a cgi by simply changing the path to reflect this ? Thanks for your tolerance. This site serves students so it's all in a good cause (read no budget) Paul Kneipp.