Email systems are platforms that allow users to send, receive, and manage electronic messages over the internet. They typically consist of a user interface, a mail server, and protocols like SMTP (Simple Mail Transfer Protocol) for sending emails and IMAP (Internet Message Access Protocol) or POP3 (Post Office Protocol) for retrieving them. These systems can be accessed through web browsers or dedicated applications on computers and mobile devices. Popular email services include Gmail, Outlook, and Yahoo Mail. Email systems also often include features like spam filtering, contact management, and calendar integration to enhance user experience.