SMTP · Example Payload

Smtp Session Example

A complete SMTP session example demonstrating the RFC 5321 command/response flow for sending an email

SMTPEmailInternet StandardsIETFMessagingProtocolsRFC 5321

Smtp Session Example is an example object payload from SMTP, with 5 top-level fields. It illustrates the shape of data this provider's APIs accept or return.

Top-level fields

descriptionstandardportsecuritysession

Example Payload

{
  "description": "A complete SMTP session example demonstrating the RFC 5321 command/response flow for sending an email",
  "standard": "RFC 5321",
  "port": 587,
  "security": "STARTTLS",
  "session": [
    {
      "direction": "server",
      "data": "220 mail.example.com ESMTP Postfix",
      "note": "Server greeting (220 = Service Ready)"
    },
    {
      "direction": "client",
      "data": "EHLO client.sender.com",
      "note": "Client identification using Extended HELLO"
    },
    {
      "direction": "server",
      "data": "250-mail.example.com\n250-PIPELINING\n250-SIZE 52428800\n250-STARTTLS\n250-AUTH LOGIN PLAIN\n250-8BITMIME\n250 SMTPUTF8",
      "note": "Server capabilities list (250 = Requested action completed)"
    },
    {
      "direction": "client",
      "data": "STARTTLS",
      "note": "Request TLS upgrade"
    },
    {
      "direction": "server",
      "data": "220 2.0.0 Ready to start TLS",
      "note": "TLS negotiation begins"
    },
    {
      "note": "[ TLS handshake occurs ]"
    },
    {
      "direction": "client",
      "data": "EHLO client.sender.com",
      "note": "Re-identify after TLS establishment"
    },
    {
      "direction": "server",
      "data": "250-mail.example.com\n250-AUTH LOGIN PLAIN\n250-8BITMIME\n250 SMTPUTF8"
    },
    {
      "direction": "client",
      "data": "AUTH PLAIN dXNlcm5hbWUAdXNlcm5hbWUAcGFzc3dvcmQ=",
      "note": "SASL PLAIN authentication (base64 encoded)"
    },
    {
      "direction": "server",
      "data": "235 2.7.0 Authentication successful"
    },
    {
      "direction": "client",
      "data": "MAIL FROM:<alice@sender.com>",
      "note": "Begin mail transaction - specify envelope sender"
    },
    {
      "direction": "server",
      "data": "250 2.1.0 Ok",
      "note": "Sender accepted"
    },
    {
      "direction": "client",
      "data": "RCPT TO:<bob@example.com>",
      "note": "Specify envelope recipient"
    },
    {
      "direction": "server",
      "data": "250 2.1.5 Ok",
      "note": "Recipient accepted"
    },
    {
      "direction": "client",
      "data": "DATA",
      "note": "Begin message data transfer"
    },
    {
      "direction": "server",
      "data": "354 End data with <CR><LF>.<CR><LF>",
      "note": "Ready to receive message data"
    },
    {
      "direction": "client",
      "data": "From: Alice Smith <alice@sender.com>\r\nTo: Bob Jones <bob@example.com>\r\nSubject: Hello from SMTP\r\nDate: Fri, 02 May 2026 10:00:00 +0000\r\nMessage-ID: <20260502100000.abc123@sender.com>\r\nMIME-Version: 1.0\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nHi Bob,\r\n\r\nThis is a test email sent via SMTP per RFC 5321.\r\n\r\nBest regards,\r\nAlice\r\n.",
      "note": "Full RFC 5322 message terminated by <CRLF>.<CRLF>"
    },
    {
      "direction": "server",
      "data": "250 2.0.0 Ok: queued as A1B2C3D4E5",
      "note": "Message accepted and queued for delivery"
    },
    {
      "direction": "client",
      "data": "QUIT",
      "note": "End session"
    },
    {
      "direction": "server",
      "data": "221 2.0.0 Bye",
      "note": "Connection closing (221 = Service closing)"
    }
  ]
}