SMTP · Schema

SMTP Session

Schema representing an SMTP protocol session as defined in RFC 5321

SMTPEmailInternet StandardsIETFMessagingProtocolsRFC 5321

Properties

Name	Type	Description
host	string	SMTP server hostname or IP address
port	integer	TCP port number
secure	string	TLS/SSL security mode. Port 465 uses TLS, port 587 uses STARTTLS
authentication	object
clientHostname	string	The client's FQDN sent in EHLO/HELO command
extensions	array	ESMTP extensions supported by the server (from EHLO response)
transaction	object

View JSON Schema on GitHub

JSON Schema

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://smtp.standard/schemas/session",
  "title": "SMTP Session",
  "description": "Schema representing an SMTP protocol session as defined in RFC 5321",
  "type": "object",
  "properties": {
    "host": {
      "type": "string",
      "description": "SMTP server hostname or IP address"
    },
    "port": {
      "type": "integer",
      "description": "TCP port number",
      "examples": [25, 465, 587],
      "default": 25
    },
    "secure": {
      "type": "string",
      "enum": ["none", "tls", "starttls"],
      "description": "TLS/SSL security mode. Port 465 uses TLS, port 587 uses STARTTLS"
    },
    "authentication": {
      "$ref": "#/definitions/Authentication"
    },
    "clientHostname": {
      "type": "string",
      "description": "The client's FQDN sent in EHLO/HELO command"
    },
    "extensions": {
      "type": "array",
      "description": "ESMTP extensions supported by the server (from EHLO response)",
      "items": {
        "type": "string"
      },
      "examples": [["STARTTLS", "AUTH LOGIN PLAIN", "8BITMIME", "PIPELINING", "SIZE 52428800"]]
    },
    "transaction": {
      "$ref": "#/definitions/Transaction"
    }
  },
  "definitions": {
    "Authentication": {
      "type": "object",
      "properties": {
        "mechanism": {
          "type": "string",
          "enum": ["PLAIN", "LOGIN", "CRAM-MD5", "DIGEST-MD5", "XOAUTH2"],
          "description": "SASL authentication mechanism"
        },
        "username": {
          "type": "string",
          "description": "Authentication username"
        }
      }
    },
    "Transaction": {
      "type": "object",
      "description": "A single SMTP mail transaction (MAIL FROM through DATA)",
      "properties": {
        "from": {
          "type": "string",
          "format": "email",
          "description": "Envelope sender (MAIL FROM command)"
        },
        "recipients": {
          "type": "array",
          "description": "Envelope recipients (RCPT TO commands)",
          "items": {
            "type": "string",
            "format": "email"
          },
          "minItems": 1
        },
        "messageSize": {
          "type": "integer",
          "description": "Estimated message size in bytes"
        }
      }
    },
    "SMTPCommand": {
      "type": "object",
      "properties": {
        "command": {
          "type": "string",
          "enum": ["EHLO", "HELO", "MAIL", "RCPT", "DATA", "RSET", "VRFY", "EXPN", "NOOP", "QUIT", "STARTTLS", "AUTH"],
          "description": "SMTP command verb"
        },
        "parameters": {
          "type": "string",
          "description": "Command parameters (e.g., FROM:<[email protected]>)"
        }
      }
    },
    "SMTPResponse": {
      "type": "object",
      "properties": {
        "code": {
          "type": "integer",
          "description": "Three-digit SMTP response code",
          "minimum": 100,
          "maximum": 599
        },
        "message": {
          "type": "string",
          "description": "Human-readable response message"
        },
        "enhanced": {
          "type": "string",
          "pattern": "^[245]\\.[0-9]+\\.[0-9]+$",
          "description": "Enhanced status code (RFC 3463) e.g., 2.0.0, 5.1.1"
        }
      }
    }
  }
}