A Mail User Agent (MUA), also known as an email client, is a software application or program that enables users to compose, send, receive, read, and manage email messages. MUAs are the interface through which individuals interact with their email accounts.
These email clients come in various forms, ranging from desktop applications to web-based interfaces and mobile apps. Some well-known examples of MUAs include Microsoft Outlook, Mozilla Thunderbird, Apple Mail, Gmail, and Yahoo Mail.