solaris9 sendmail query

[nyck]

Hello,

I have the following entry in my /etc/mail/sendmail.cf file:-

# "Smart" relay host (may be null)
DSmailhost$?m.$m$.

So how does this above entry know which mail relay to use?

If the first mail relay is down would sendmail just default to the next one in the list, if so how?

cheers

nick