laravel_sketch/app/Mail/RegisterEmail.php

<?php

namespace App\Mail;

use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;

class RegisterEmail extends Mailable
{
    use Queueable, SerializesModels;

    public $code;
    public $subject = "您的注册验证码";
    /**
     * @param $code
     */
    public function __construct($code)
    {
        $this->code = $code;
    }

    /**
     * Build the message.
     *
     * @return $this
     */
    public function build()
    {
        return $this->view('emails.register');
    }
}