What is SMTP?
SMTP, or Simple Mail Transfer Protocol, is an internet protocol used for sending email messages between servers over the internet. As part of the TCP/IP protocol, SMTP is hugely important in all email transactions.
SMTP is responsible for transferring the email files from the sender’s email client to the email server. SMTP communicates with the Mail Transfer Agent (MTA) to ensure that your email communication is sent to the right email server, and the right email address.
SMTP uses ports 25, 587, or 465 to send emails to remote mail servers.