You should start with a quality list not quantity. Your target audiences should VERY VERY relate with the topic you are sending out.
If you are sending email regarding selling properties, you must have a list of property owners who are selling their condo, houses or lands. If you are sending email about Omega Speed Master Moon Watch , you should have a list of watch lovers.
People tend to open email if the email is related with WHAT they are interesting in the meantime . I never open email regarding Viagra because I don't have such a problem (Do you?). Don't just send email to anybody. If possible,you should personalize your email for each recipient, that will generate the best results.
House lists generate the best e-mail marketing results. So how do you grow your house list? You must offer them some benefits ( I mean some useful stuffs) such as project progress, promotion of the month, market analysis - you name it. Don't provide them special offers or special deals otherwise you will get only junk email addresses from those who just want those special offers.We need quality not quantity.