| type | 'attachment' | | Message type |
| content | any | | Attachment contents |
| contentType | string | | MIME type of the message |
| contentDisposition | string | | Content disposition type for the attachment |
| filename | string / undefined | <optional> | File name of the attachment |
| headers | Headers | | A Map value that holds MIME headers for the attachment node |
| headerLines | HeaderLines | | An array of raw header lines for the attachment node |
| checksum | string | | A MD5 hash of the message content |
| size | number | | Message size in bytes |
| contentId | string / undefined | <optional> | The header value from Content-ID |
| cid | string / undefined | <optional> | contentId without < and > |
| related | boolean / undefined | <optional> | If true then this attachment should not be offered for download |