For example, if you set up an autoresponder with an interval of 24 and you receive an email from email@example.com at 8:00 AM on Monday, the autoresponder immediately responds to the message. If, however, firstname.lastname@example.org continues to email you throughout the day, the autoresponder does not send another response for 24 hours after the initial email (in this case, 8:00 AM on Tuesday). If email@example.com emails you again after the 24-hour interval expires, the system sends them an autoresponse.
However, as email marketing developed as an effective means of direct communication, in the 1990s, users increasingly began referring to it as "spam", and began blocking out content from emails with filters and blocking programs. In order to effectively communicate a message through email, marketers had to develop a way of pushing content through to the end user, without being cut out by automatic filters and spam removing software.
In addition to satisfying legal requirements, email service providers (ESPs) began to help customers establish and manage their own email marketing campaigns. The service providers supply email templates and general best practices, as well as methods for handling subscriptions and cancellations automatically. Some ESPs will provide insight and assistance with deliverability issues for major email providers. They also provide statistics pertaining to the number of messages received and opened, and whether the recipients clicked on any links within the messages.