[Bug]: artisan mail:webhooks fails

### What happened?

<img width="650" height="288" alt="Image" src="https://github.com/user-attachments/assets/6153fd25-d71c-4811-90bd-c328f8670990" />

### How to reproduce the bug

Run `php artisan mail:webhooks postmark`

### Package Version

5.1.1

### PHP Version

8.4.23

### Laravel Version

12.61.0

### Which operating systems does with happen with?

macOS

### Notes

_No response_