Sendmail: Configure to use a smart host

[ATC]

My Linux server is behind a firewall and is not allowed to send internet email but must do so via another SMTP server in my network. How can I configure sendmail to do so?

[ATC]

Edit /etc/mail/sendmail.cf with the following:
"DShost.domain.com"
where "host.domain.com" is the fully qualified host name of your DMTP smart host. Make sure your server can resolve this host name to an IP address and confirm that it can connect to TCP port 25.

Restart sendmail with "service sendmail reload" (or similar)