SMTP and POP3 are protocols used to facilitate email traffic between computers. Every time an email is sent it goes through a set of protocols that ensure security and allow conversation between the client and the host. SMTP is used along side of POP3 in a workplace environment. SMTP is short for Simple Mail Transfer Protocol and allows the email client to send emails to the server. Using port 25, SMTP connects to the email server and sends information to the server. The server receives the emails and processes where to send them.