mail archive file

Currently my Smartlist saves mail archive with permission 660 and
group of the list account, like in:

-rw-rw----    1 slist    slist          1860 Jun  6 09:38 4298

How may I change it to save with permission 644 or with a
different group? (I have already made ~slist a member of another
group), like in

-rw-r--r--    1 slist    slist          1860 Jun  6 09:38 4298
-rw-rw----    1 slist    web            1860 Jun  6 09:38 4298

I guess it would be somewhere in rc.submit but appreciate any hint.

Thanks,
Zhiliang