A text, video, graphic, PDF or sound file that accompanies an email message but is not included in the message itself. Attachments are not a good way to send email newsletters because many ISPs, email clients and individual email recipients do not allow attachments, because hackers use them to deliver viruses and other malicious code.

Building a Highly-targeted Opt in List: When Money Lies Beneath the Lists
Are you successful with your Internet business? Better yet, do you think you are successful with your online business? When most online entrepreneurs are asked with these questions, they often brush it off.