Want sendmail applying aliases to 'cc:' field too

[c0re]

Hey all!

I've got /etc/mail/aliases file like

user: user at site1.domain.com
user2: user2 at site1.domain.com
user3: user3 at site2.domain.com

When someone from Internet send email to user at domain.com with cc: to
user3 at domain.com sendmail send mail to user and user3 normaly, they
recieve their mail.

But I need some additional behavior:
user receive that mail with

to: user at site1.domain.com
cc: user3 at domain.com

I want that cc would be user3 at site2.domain.com, like in aliases file.

Because I got problems replying to all (with user3 at domain.com
included, but it must be user3 at site2.domain.com). How this can be
achieved?

In other words I need some kind of cc: field rewriting regarding to
aliases file contents.

I have not found such feature in sendmail. So I think this can be done
with some milter may be... Anyone has ideas?

Any tips, thinks, tricks and etc highly needed! I'm out of ideas at that moment.

Thanks!