Red Hat Enterprise Linux 5 Administration Unleashed

Understanding Email Concepts 369Sender’s MUAInternetMTA ServerIMAP ServerRecipient’s MUA18FIGURE 18.2Sending an Internal EmailTo read the email, the recipient uses an MUA, commonly known as an email client. Itmust be configured to download the email using a protocol accepted by the MTA storingthe email. Most MTAs accept the POP3 protocol, the IMAP protocol, or both. The differencesbetween these two protocols are discussed later in the “Using POP and IMAP”section.After the recipient reads the email, he has many options. For example, he can choose tomake a copy of it on his local filesystem, keep the message on the server, delete themessage from the server, forward the email to a different person, or reply to the personwho sent the email.