umask are the default permissions that are applied when a file or directory are created. To see this in action simply just "touch filename" or "mkdir somedir" and you'll see what default permissions are applied.
The first thing Ialways tell people you should know is to NEVER change the defaults unless you are making them more restrictive. But they work well and if you change the defaults you could end up creating a file without permission to read........
Aug 25 16:43:24 evohostingtor postfix/master: fatal: /etc/postfix/master.cf: line 24: field "unprivileged": bad value: "???"
Solution: I had the wrong thick dashes when c&ping (just retype them with your keyboard)
Aug 25 16:47:10 mailbox postfix/master: fatal: /etc/postfix/master.cf: line 25: bad transport type: syslog_name=postfix/auth-cleanup
auth-cleanup unix n - - - 0 cleanup