| attachments | Attachment[] | | An array of attachment |
| headers | Headers | | A Map object with lowercase header keys |
| headerLines | HeaderLines | | An array of raw header lines |
| html | string / false | | The HTML body of the message. Sets to false when there is no HTML body |
| text | string / undefined | <optional> | The plaintext body of the message |
| textAsHtml | string / undefined | <optional> | The plaintext body of the message formatted as HTML |
| subject | string / undefined | <optional> | The subject line |
| references | string[] / string / undefined | <optional> | Either an array of two or more referenced Message-ID values or a single Message-ID value |
| date | Date / undefined | <optional> | A Date object for the Date: header |
| to | AddressObject / AddressObject[] / undefined | <optional> | An address object or array of address objects for the To: header |
| from | AddressObject / undefined | <optional> | An address object for the From: header |
| cc | AddressObject / AddressObject[] / undefined | <optional> | An address object or array of address objects for the Cc: header |
| bcc | AddressObject / AddressObject[] / undefined | <optional> | An address object or array of address objects for the Bcc: header |
| replyTo | AddressObject / undefined | <optional> | An address object for the Reply-To: header |
| messageId | string / undefined | <optional> | The Message-ID value string |
| inReplyTo | string / undefined | <optional> | The In-Reply-To value string |
| priority | 'normal' / 'low' / 'high' / undefined | <optional> | Priority of the e-mail |