Getting your messages delivered to the right prospect at their right address is as important as planning your marketing campaigns. Having a comprehensive email list is not going to serve your purpose. If the list of your targeted audience is filled with old and incomplete details then you end up screwing up your campaign productivity. Hence, frequent cleaning has to be done for maintaining the quality and responsiveness of the list.
Infographic Source: https://www.infoclutch.com/infographic/why-email-list-hygiene-so-important