Microsoft Certified Systems Engineer (MCSE) Question:

SMTP or Simple Mail Transfer Protocol is used to send email messages between servers. The messages are retrieved using email clients. SMTP is more commonly used to send messages from a mail client to a mail server. And hence the email client like POP needs to be configured. Hence, SMTP is used to send emails while POP or IMAP are used to receive messages. It is usually operated on port25 on the internet.