The delivery of e-mails you send to a high percentage of recipients is directly related to your IP address and domain reputation. If you have a high score, Internet Service Providers (ISPs) will trust your reputation and ensure that your e-mails reach the recipients without dropping into the spam box. Your e-mail deliverability depends on your high IP reputation, and to ensure this you should;

Proceed by using the double-opt-in method by confirming that your recipients are real and relevant people, and forwarding your content to the relevant people increases your IP reputation by reducing the possibility of being marked as spam.
Organize your e-mail list by at first sending your e-mails to a small and relevant group, and then trying to slowly grow your list.