Is this a mail bug ?

[Dong Chen]

This seems a bug for me.
After I change my LOGNAME to somebody else's name,
I can actually read all his mails using "Mail".
While I cannot read /usr/mail/foo directly.
here is what it's like:

%setenv LOGNAME foo
%Mail
Mail version 5.2 6/21/85.  Type ? for help.
"/usr/mail/foo": 2 messages 2 unread [Read only]
>U  1 *******
 U  2 *******
& q
%more /usr/mail/foo
/usr/mail/foo: Permission denied
%ls -l /usr/mail/foo
-rw-rw----   1 foo      mail        2338 May  9 14:02 /usr/mail/foo

After I changed the mode to 600, others cannot read the mail.
But since the default one is 660, I don't know if there are potential problem
to change it to 660 ?