I would like to use OpenBSD 4.3 with it's default Sendmail installation
just as a backup MX server. So this server will be listed in the DNS as
the 2nd MX record with a higher MX number as the first MX record.

Now I changed the sendmail_flags in rc.conf.local to "-L sm-mta
-C/etc/mail/sendmail.cf -bd -q30m" so that the port 25 is available from
outside and added the domains which need secondary MX in the

Is this all I need to do ? Or did I miss something ?