From a discussion on JWZ's blog, came the suggestion:

X-Sender: info@evite.com
From: <info@evite.com>

If that's in every message, try this in your .m4 or .mc file:

 LOCAL_RULESETS
 HX-Sender: $>Check_XSender
 D{MPat}info@evite.com
 D{MMsg}Spamming denied
 SCheck_XSender
 R${MPat} $* $#error $: 553 ${MMsg}
 RX-Sender: ${MPat} $* $#error $: 553 ${MMsg}

There are tabs betwen $* and $#.

And the follow-up:

<shodan> I'm kinda surprised that after all this time, sendmail's config is still based on ancient hieroglyphs
<shodan> . o O ( To enable sender-validation in sendmail, enable this option: bird, squiggley line, sideways man, fish )