Marketo can provide the inferred Company, City, State/Region, Postal Code, Country, Metro Area, and Area Code from the IP address of a webpage visitor.
I haven't used LeadLander, but they cannot infer/know a specific email address from the IP address of a webpage visitor. I visited their website and discovered that they do provide a list of Jigsaw and LinkedIn contacts based on the Inferred company of the person that visited your website. Marketo does not do this, but if you are already a Marketo user, it would probably make more sense to contract with these data vendors directly. In fact, Marketo has a Enrich with Data.com flow action if you are a subscriber to that service (we are).