Sendmail Configuration to not deliver mail to local machine

If you are playing the "sendmail.mc" game:

define(`SMART_HOST',`smtp.your.provider')

If you hack sendmail.cf directly:

DSsmtp.your.provider

...but if you hack sendmail.cf directly you probably already knew that.

This tells the system that for accounts in its own domain that it doesn't directly know about, send mail to smtp.your.provider which presumably knows what to do with it. Note that accounts that it does know about (ie root) will need to be aliased to a non-local account or messages to root will be delivered locally.

You can use FEATURE(nullclient). Or, you can change ruleset 0 to do the same thing.