Download an attachment
GET
/api/v1/messages/{id}/attachments/{aid}
Responses
Attachment bytes, decoded. Always sent as Content-Type: application/octet-stream, whatever the stored content_type (read that from the attachment list), with Content-Disposition: attachment; filename="<name>", where every character outside A-Z a-z 0-9 . _ - is replaced by _ and a part with no filename is named attachment. Also sent with Cache-Control: private, max-age=31536000, immutable and X-Content-Type-Options: nosniff, and never compressed.
application/octet-stream
GET
/api/v1/messages/{id}/attachments/{aid}