SMTP is the core protocol used for sending email and transferring messages between mail servers. When you click Send in an email application, the message is normally submitted to a mail server through SMTP.
What does SMTP do?
SMTP accepts a message from the sender and attempts to deliver it to the destination mail server. Incoming email is normally accessed through protocols such as IMAP or POP3.
What is an SMTP server?
An SMTP server receives outgoing messages, performs required checks and attempts delivery to the recipient’s mail system.
SMTP authentication
Business email systems normally require users to authenticate before sending mail. This helps prevent unauthorized people from using the server to send spam.
Why is TLS important?
TLS helps encrypt communication between an email client and the SMTP server. Secure connections are particularly important when account credentials are transmitted.
SMTP and deliverability
A successful SMTP submission does not guarantee inbox delivery. Domain reputation, IP reputation, SPF, DKIM, DMARC and message content can all influence deliverability.
Read more: What Is Email Deliverability?
Conclusion
SMTP is one of the fundamental technologies behind internet email. Secure authentication, TLS and correct DNS configuration are essential for reliable business email delivery.