Purchased lists are ineffective, and they impact everyone else who uses Mailchimp, too. If you send emails to a list of people whose contact info you bought, many of the emails will get identified as spam. Some spam filters will flag a campaign if anyone with the same IP has sent spam in the past. When you use Mailchimp, your email is delivered through our servers, so if one person sends spam, it could prevent other users’ emails from reaching inboxes. But by forbidding Mailchimp users from using purchased lists, we increase deliverability for everyone.
When it comes to deciding how to craft that perfect subject line, there appears to be really only one area to avoid: the subject line of 60 to 70 characters. Marketers refer to this as the “dead zone” of subject length. According to research by Adestra, which tracked over 900 million emails for its report, there is no increase in either open rate or clickthroughs at this 60-to-70 character length of subject line.