[exim] how to set up smtp AUTH

Hi,

New to the list..

I am trying to set up Exim to use SMTP Auth on my VPS. I have found
various instructions, including some set by the support department by my
provider. It simply does not work. Instructions provided were:

$ chgrp exim /etc/shadow
$ chmod g+r /etc/shadow

Add the following block of text to the authenticators section of your
exim.conf:

plain:
driver = plaintext
public_name = PLAIN
server_prompts = :
server_set_id = $2
server_condition = "${if pam{$2:$3}{1}{0}}"

login:
driver = plaintext
public_name = LOGIN
server_prompts = "Username:: : Password::"
server_set_id = $1
server_condition = "${if pam{$1:$2}{1}{0}}"

Taken from:
http://www.tipcache.com/tip/Setup_SMTP_AUTH_and_TLS_with_Exim_8.html

Now I can't get past 'step 1' - chgrp exim /etc/shadow

There is no group called exim. How can proceed to get this to work?

Thanks,

Kevin