You can't really do anything with anonymous visitors except track their behaviour in munchkin and have the last three months associated with the person when they become known. Once someone becomes known you can use their munchkin data to perform actions.
on the Marketo ABM documentation I found this though:
- The Account Based Marketing module allows you to upload a CSV file or Synch from your CRM all your target accounts and set flows that will be triggered once you have visitors on your webpage from these companies - anonymous and known. You can then send daily reports or configure email alerts to be sent automatically to your sales teams
So, while I can´t send them directly emails I still can know that the visitor from a Company X has visited my website. Correct?
It's quite limited what you can do in terms of triggers based on anonymous activity, but yes you'll be able to know if an anonymous person from a target account has visited your site.