The primary function of an email server in communications is to send, receive, and store email messages. Email servers operate using specific protocols, such as SMTP (Simple Mail Transfer Protocol) for sending emails and IMAP (Internet Message Access Protocol) or POP3 (Post Office Protocol) for receiving them. These servers manage the storage and retrieval of messages, ensuring that emails are delivered to the correct recipients. Furthermore, they provide essential security features to protect sensitive information during transmission.