The percentage of people who pass on a message or file.
Pass-along rates are a measure of word-of-mouth marketing. Objects typically passed include email messages, Web pages and multimedia files. Content typically passed includes humor and entertainment, late-breaking news, shopping specials, and technical gizmos.
see also: Digital Marketing Tools
Udemy: Email Marketing – learn email marketing with online courses.
How-To Do Viral Marketing: The Ultimate Archive of Videos & Podcasts
MarketingTerms.com (February 15, 2012)