Simple Mail Transfer Protocol (SMTP)

What is Simple Mail Transfer Protocol (SMTP)?

SMTP (Simple Mail Transfer Protocol) is the standard protocol that computers use to send and route email across the internet from one server to another.

Think of SMTP as the digital postal service. While other protocols are responsible for receiving mail, SMTP is the carrier that picks up your message and delivers it toward the recipient's mail server.

How does SMTP work?

When you hit "send", your email does not fly straight to the recipient's inbox. Instead, it passes through a series of steps between servers:

1. Submission: Your email client connects to your configured SMTP server.
2. Handshake: The client and server identify themselves, and the server verifies the sender is authorized.
3. Routing: The server looks at the recipient's domain and finds the destination server.
4. Transfer: The servers move the data using SMTP commands.
5. Delivery: The email is dropped at the recipient's server, where it waits to be collected.

What are the common SMTP ports?

Servers communicate over specific ports, depending on security needs:

• Port 25: The original port, now mostly used for server-to-server communication and often blocked by ISPs.
• Port 587: The modern standard for email submission, usually paired with TLS encryption.
• Port 465: Originally for "SMTPS", still used by some systems for secure connections.

SMTP and MIDAS

MIDAS supports sending email via an SMTP server or relay in both cloud and self-hosted editions. The other available email sending options are Sendmail (for self-hosted editions) and "Cloud" (for cloud-hosted editions from v4.42 onwards).