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Internet Message Access Protocol (IMAP)
Another protocol that is used to retrieve emails from an email server is known as IMAP. IMAP operates on port 143 and, similar to POP, IMAP downloads a copy of the email messages from the server and the messages as access through an email client, such as Microsoft Outlook or Mozilla Thunderbird:
IMAP does not automatically deletes email messages from the email server. To delete an email from the email server requires manual intervention.