An inactive subscriber is a newsletter subscriber who has been observed as inactive for a certain amount of time.
Each email marketer has his own criteria and threshold to determine when a subscriber is considered as inactive. Inactivity definition is based on the action taken into account - typically an opening or a click - and on the length of inactivity - expressed by a time length or number of received messages.
For instance, an inactive subscriber can be defined as a suscriber who had not clicked through an email link for six months - or for the last thirty messages.
Inactivity criteria must be determined according to the type of activity and the nature of emails.
Inactive subscriber management relates to several issues:
Two many inactive subscribers may be a danger for campaign deliverability as they could use the spam button in the future and especially because spam and folder filtering is more and more often based on receivers’ behavior.
Inactive subscribers who can be reactivated may be a source of additional revenue.
Campaign metrics are flawed by two many old inactive subscribers. Thus, low opening and click rates may be due to ghost subscribers and not really to a content issue.
Inactive subcribers who can’t be reactivated are a useless cost, but this cost is often seen as negligible.
Inactive subscribers are managed through reactivation and list cleaning campaigns which allow marketers to reactivate some subscribers and to suppress definitive inactive subscribers.