SMTP · Schema

SMTP Email Message

Schema representing an email message as defined by RFC 5321 (SMTP) and RFC 5322 (Internet Message Format)

SMTPEmailInternet StandardsIETFMessagingProtocolsRFC 5321

Properties

Name	Type	Description
from	string	The sender's email address (RFC 5322 From header / SMTP MAIL FROM)
to	object	Recipient address(es) (RFC 5322 To header / SMTP RCPT TO)
cc	object	Carbon copy recipient(s)
bcc	object	Blind carbon copy recipient(s) - not included in message headers
replyTo	string	Reply-To address if different from From
subject	string	Email subject line (RFC 5322 Subject header)
date	string	Message creation date and time (RFC 5322 Date header)
messageId	string	Unique message identifier in format (RFC 5322 Message-ID)
body	object
headers	object	Additional RFC 5322 headers as key-value pairs
attachments	array	MIME attachments

View JSON Schema on GitHub

JSON Schema

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://smtp.standard/schemas/message",
  "title": "SMTP Email Message",
  "description": "Schema representing an email message as defined by RFC 5321 (SMTP) and RFC 5322 (Internet Message Format)",
  "type": "object",
  "required": ["from", "to", "subject"],
  "properties": {
    "from": {
      "type": "string",
      "format": "email",
      "description": "The sender's email address (RFC 5322 From header / SMTP MAIL FROM)"
    },
    "to": {
      "oneOf": [
        {"type": "string", "format": "email"},
        {
          "type": "array",
          "items": {"type": "string", "format": "email"},
          "minItems": 1
        }
      ],
      "description": "Recipient address(es) (RFC 5322 To header / SMTP RCPT TO)"
    },
    "cc": {
      "oneOf": [
        {"type": "string", "format": "email"},
        {
          "type": "array",
          "items": {"type": "string", "format": "email"}
        }
      ],
      "description": "Carbon copy recipient(s)"
    },
    "bcc": {
      "oneOf": [
        {"type": "string", "format": "email"},
        {
          "type": "array",
          "items": {"type": "string", "format": "email"}
        }
      ],
      "description": "Blind carbon copy recipient(s) - not included in message headers"
    },
    "replyTo": {
      "type": "string",
      "format": "email",
      "description": "Reply-To address if different from From"
    },
    "subject": {
      "type": "string",
      "description": "Email subject line (RFC 5322 Subject header)"
    },
    "date": {
      "type": "string",
      "format": "date-time",
      "description": "Message creation date and time (RFC 5322 Date header)"
    },
    "messageId": {
      "type": "string",
      "description": "Unique message identifier in format <local@domain> (RFC 5322 Message-ID)"
    },
    "body": {
      "$ref": "#/definitions/MessageBody"
    },
    "headers": {
      "type": "object",
      "description": "Additional RFC 5322 headers as key-value pairs",
      "additionalProperties": {"type": "string"}
    },
    "attachments": {
      "type": "array",
      "description": "MIME attachments",
      "items": {
        "$ref": "#/definitions/Attachment"
      }
    }
  },
  "definitions": {
    "MessageBody": {
      "type": "object",
      "description": "The message body content",
      "properties": {
        "text": {
          "type": "string",
          "description": "Plain text body (text/plain MIME part)"
        },
        "html": {
          "type": "string",
          "description": "HTML body (text/html MIME part)"
        },
        "mimeType": {
          "type": "string",
          "description": "MIME content type for multipart messages",
          "examples": ["multipart/mixed", "multipart/alternative", "text/plain", "text/html"]
        }
      }
    },
    "Attachment": {
      "type": "object",
      "required": ["filename", "contentType"],
      "properties": {
        "filename": {
          "type": "string",
          "description": "Attachment filename"
        },
        "contentType": {
          "type": "string",
          "description": "MIME content type (e.g., application/pdf, image/png)"
        },
        "contentId": {
          "type": "string",
          "description": "Content-ID for inline attachments"
        },
        "disposition": {
          "type": "string",
          "enum": ["attachment", "inline"],
          "description": "Content disposition type"
        },
        "size": {
          "type": "integer",
          "description": "File size in bytes"
        }
      }
    }
  }
}