[Exim] Exim - /var/mail directory

Hi !

I have a problem with exim (3.34 - Solaris/Sparc).

Server (solaris 8/sparc)
------------------------

When I send a message to test user, Exim creates in /var/mail
user file:

xxx:~$ ls -l /var/mail | grep test
-rw-------   1 test    emp         1000 Jan 31 08:22 test
 --                    ---
                        ^
                        |
                       where emp is primary group of test user

and privileges 600 for it.

Privileges /var/mail directory on this server:

xxx:~$ ls -l /var | grep mail
drwxrwsrwx    2 root     mail         4096 Jan 30 11:00 mail
      -                  ----

On other server (Debian) I have:
--------------------------------

zzz:~$ ls -l /var | grep mail
drwxrwsr-x    2 root     mail         4096 Jan 30 11:00 mail
    ------               ----

and when I send a message to test user I get in /var/mail
file:

main:~$ ls -l /var/mail | grep test
-rw-rw----    1 test      mail          554 Jan 29 10:28 test
 -- --                    ----

I have a question, where can I set up it ? I don't found this option
in Makefile. I tried to set EXIM_GROUP=6 (where 6 is GID mail group)
in Makefile and recompile Exim, but without good results.

Please help me.

Thank you

Sławek