A mailing list archive is a collection of past messages from one or more electronic mailing lists. Such archives often include searching and indexing functionality. Many archives are directly associated with the mailing list, but some organizations, such as Gmane, collect archives from multiple mailing lists hosted at different organizations; thus, one message sent to one popular mailing list may end up in many different archives. Gmane had over 9,000 mailing list archives as of 16 January 2007. Some popular free software programs for collecting mailing list archives are Hypermail, MHonArc, and FUDforum.
A tracking pixel is a snippet of code that allows you to track your subscribers’ activity across various channels like your website, landing pages, and newsletters. Then, you also have the option to send emails triggered by certain behaviors. So for example, if a subscriber goes to your site and checks out your product page, a tracking pixel can send an email with a special offer for the specific product the viewed.