URI canonicalization whitelist

Is there an easy way to skip,

  dbg: uri: added host: from.condocerts.com domain: condocerts.com
  dbg: dns: found CNAME sparkpostmail.com for host from.condocerts.com
  dbg: uri: canonicalizing parsed uri: sparkpostmail.com
  dbg: uri: cleaned uri: sparkpostmail.com

for certain URIs?

Ideally condocerts.com would not host their subdomains with well-known
spammers, but that's not up to me. Instead what I think I'd like to do
is not canonicalize condocerts.com.