class-dump Mail.app generates Unknown load command: 0x00000032

I'm trying to do some reverse engineering on the MacOS's Mail.app. For this, I'm using class-dump, but I receive the following output:

Silviu:~ silviu$ class-dump /System/Applications/Mail.app
2020-04-08 10:54:36.536 class-dump[52413:2202003] Unknown load command: 0x00000032
//
//     Generated by class-dump 3.5 (64 bit).
//
//     class-dump is Copyright (C) 1997-1998, 2000-2001, 2004-2013 by Steve Nygard.
//

#pragma mark -

//
// File: /System/Applications/Mail.app/Contents/MacOS/Mail
// UUID: 7C43215A-CB02-3FF4-9559-20231135B148
//
//                           Arch: x86_64
//                 Source version: 3608.40.2.2.4
//

//
// This file does not contain any Objective-C runtime information.
//

I cannot believe that there does not exist some Objective-C stuff.