Hey @Kez_JoJo
Welcome to the community 
You can absolutely start capturing users to a mailing list.
I would typically use a 3rd party mailing platform like mailchimp, to capture these and send them directly to a list over there. Details on that here
In regards to the login etc, this is not something that is currently supported natively by webflow so you would need to sort of ‘hack’ this together. There are a few forum posts on guides to intergrate these kind of systems.
Hope that helps man,
Tom