In Internet, an email client, email reader or more formally mail user agent (MUA) is a computer program in the category of groupware environments used to access and manage a user's email.

Client is meant to be a role. For example, a web application which provides message management, composition, and reception functions may internally act as an email client; as a whole, it is commonly referred to as webmail. Likewise, email client may be referred to a piece of computer hardware or software whose primary or most visible role is to work as an email client.