Ongoing campaigns are an important form of customer dialogue in email marketing. They work especially well when linked together into one or more email series.
An ongoing campaign allows you to send behavior-based emails to selected recipients, independent of the regular newsletters you are sending out.
The mailing is sent daily with the same content to recipients of an auto-update segment. Because the segment updates itself automatically according to certain terms that you set, recipients only receive the email once – right at the exact moment that you've determined would be best for them. A typical ongoing campaign would be, for example, a reminder about a previous unopened campaign (attribute set to "has received" but "hasn't opened").
Learn about auto-update segments here