How to check Field Value against a smart list

Hi there,

I'm trying to send alert to account owner, whenever anyone from @sampledomain.com visited our site.

I have domain fields created on lead/contact object in SFDC (syncing to marketo). I also have opt-in boxes on contact object for account owners to check off to indicate they want that alert. 

My only problem is how do I use this domain field check against my entire marketo database to create a smart list. or even use it to enrol people into a program.