A worthwhile house email list is the one prerequisite of any email campaign. But worthwhile does not mean big but specific. In compiling your email addresses you should target those you want and go after them, rather than passively waiting for them to contact you. This requires careful planning and dedicated execution. Your plan should not limit you to one source, or even just a few. You should go where you potential customers are rather than where it is easiest for you.
There are a variety of sources for email addresses. Each must be treated to a limited extent as a separate campaign but there will be considerable overlap. Focusing on one source alone is not normally an efficient use of resources.
You can divide your targets crudely as online and offline, or as existing customers and those unknown. But this is useful only for planning and should not obscure the fact that most will have much in common. This is axiomatic as it is you who want them and you will have specific requirements.
In other words, whilst your email addresses might come from different sources there should be a system to bring them all under one overarching plan.