Anonymous Leads becoming known

[Anonymous]

It says in a help article that other than filling in a form, an anonymous lead is merged into a new or existing known lead when someone Clicks a link in a Marketo email.

How can they have received a marketo email if they are an anonymous lead?

[Anonymous]

Hi Selene,

The article you're referring to means if someone has multiple IP addresses, is using multiple computers, or has removed cookies on their machine.  Marketo will not know that this is the same person you already have in your databse - so when they receive an email and click on it, Marketo associates the unknown, anonymous record with the known record.