A Mail User Agent (MUA) is synonymous with an email client application. An MUA is a program that, at the very least, allows a user to read and compose email messages. Many MUAs are capable of retrieving messages via the
IMAP protocols, setting up mailboxes to store messages, and sending outbound messages to an MTA.
MUAs may be graphical, such as Evolution, or have simple text-based interfaces, such as pine.