Blocking Malformed "From" Headers

I have a spammer using a malformed From header, as follows:

From: <UPS>[email protected]

The envelope from is: [email protected], and I've set up blocks 
for that address.

Sendmail is munging the From: header to change <UPS> to 
<[email protected]>, so it ends up looking like a local address to my users.

How do I detect similar mangled From headers in Spamassassin?

Also does anyone know how to prevent Sendmail from rewriting the From 
header like this?  The documentation for confFROM_HEADER is a somewhat 
cryptic:

https://www.sendmail.org/~ca/email/doc8.12/cf/m4/tweaking_config.html#confFROM_HEADER

I'd rather it say <UPS@suspected-spammer> instead, or reject it entirely.

Thanks,
Kirk