mail server location question

[Bruce Edge]

Can I run the qmail server behind a firewall?

I want to rely on the dns MX records on the firewall to route mail to the
qmail server, which is on an internal LAN, with a non Internet routable
192.168.1 address.

Will this work?, or, do I need to have the qmail server addressable from the
internet directly?

Thanks in advance, Bruce.