I have never heard of that, but I am sure there is some method to do so. But I refuse to use sendmail, and stick with postfix. Sendmail is merely a test to ones anal retentiveness, rather than a better mail service
If it is possible in sendmail, hit up their listserv and ask there or read up on their website for instructions on how to do it. The next best two ideas would be to hitup your distro's site and irc channel. Red Hat's IRC has some Gurus that know sendmail rather well and could at least point you how to do it.