amavisd-new fails to start

[Horst B Simon via macports-users]

I have installed amavisd-new successful with the latest version of macports on 
macOS HighSierra, but it fails to start with following message:
ERROR: MISSING REQUIRED ADDITIONAL MODULES:
  auto::Crypt::OpenSSL::RSA::new_public_key

After googling it says, the most common immediate workaround is to revert to an 
older, compatible version of the perl-crypt-openssl-rsa package. A more 
permanent solution to upgrade amavisd-new to work with the newer version.

Horst