What's an e$-$mail server?

An e$-$mail server is the computer to which the e$-$mail message is sent.

An e$-$mail server is the e$-$mailing software that stores, processes, and sends e$-$mails.

An e$-$mail server is a specialized computer that stores, processes, and sends e$-$mails.

An e$-$mail server is the party that decrypts the code.