If the Notes server participates in Internet mail it should have an SMTP gateway. And in that case you should be able to include:
define(`SMART_HOST', `notes.domain.tld')dnl
in your sendmail.mc (replacing notes.domain.tld with the FQDN of the Notes server) and rebuild sendmail.cf and restart sendmail. It may be necessary to also:
define(`LUSER_RELAY', `notes.domain.tld')dnl
to cause sendmail to forward mail to addresses on the Notes server that don't correspond to local accounts on the Unix box (if both are in the same domain).
define(`SMART_HOST', `notes.domain.tld')dnl
in your sendmail.mc (replacing notes.domain.tld with the FQDN of the Notes server) and rebuild sendmail.cf and restart sendmail. It may be necessary to also:
define(`LUSER_RELAY', `notes.domain.tld')dnl
to cause sendmail to forward mail to addresses on the Notes server that don't correspond to local accounts on the Unix box (if both are in the same domain).