OS X Server Postfix configuration
To check which file your postfix is using do a ps ax | grep master at the command line and you should see a line with

master -c /Library/Server/Mail/Config/postfix


which tells you that it is indeed using the files in that directory.

If it is using those files then I'd try logging in from another machine using telnet and see what is says.

telnet mailserver.example.com 25


If you want to try sending a message "by hand" then check out http://www.smtp2go.com/articles/smtp-protocol for some good notes on SMTP.

It is here that Postfix will probably reject your email. If it does reject your email then set smtpd_client_restrictions back to the default and see if it then allows your email through.