a specific email message-a promotional email, newsletter, announcement, press release, holiday greeting or other type of message sent to a list of recipients who have given you permission to email them
a email distribution to a list of email addresses. Ideally done to people who choose to receive email; i.e., The most successful email campaigns are to people who anticipate your email, recognize your name and are interested in your offer.
When you build an email and send it to your recipients this is defined as an email campaign. Your campaign may be a newsletter or may consist of offers.