What is SMTP – Simple Mail Transfer Protocol

SMTP stands for a Simple Mail Transfer Protocol. Previously we did an article on POP3 and IMAP, the protocols that are used for email retrieving. SMTP is a protocol that is used for sending emails. SMTP is basically a set of commands that authenticates and directs the transfer of email. Good way to remember what SMTP does is by looking at the acronym SMTP and associating it with Sending Mail To People.

When you write an email using an email client, such as Microsoft Outlook, and when you hit send button, the email travels from your computer to your email server using the SMTP protocol. This server is known as the SMTP server and its address is what’s configured in your email client. For example, if you’re using Gmail, the SMTP server address would be smtp.gmail.com.

SMTP server will send the message to the recipients email server also using SMTP protocol. The email will stay on the recipients email server until the recipient logs into their email account and downloads the email using POP3 or IMAP protocol.

SMTP uses the TCP protocol, which is a connection-oriented protocol. This means that it guarantees the delivery of the email. This is assuming that the destination email address is correct and still exists. If, for some reason, the email that you sent does not reach its destination (maybe you misspelled the email address or the email address no longer exists), you’ll get that familiar mail delivery error in your mailbox informing you that the email you sent failed.

Like POP3 and IMAP protocols, SMTP protocol is also configured in your email client, in the outgoing server settings. This is also known as the SMTP server setting. This setting tells your email client where it can send the email.