File creation mask. The read and write permissions set on new files are determined by the umask specified in the matching server access record.
On UNIX servers, the umask is a variable having a three-digit octal value, similar to that used by chmod, but which describes the permissions that are not to be set on new files.
On Windows servers, the umask is used to set read and write permissions for the owner (leftmost digit) and for other (rightmost digit). The group digit (middle) is ignored.