Avoid having your emails blocked by checking your mail provider rules. Most server providers prevent spam by requiring that you do not send too many emails in a short period of time. You won't be able to send more that 1000 emails with GoDaddy for example. Try to keep your email delivery rate as high as possible and avoid that your emails end up in junk or spam folders. Avoid these basic mistakes and you are on your way to a successful email marketing and list building campaign.