Error ketika send email dari mailgun

Assalamualaikum agan semunya error ini saya dapatkan ketika belajar di buku seminggu belajar laravel, saat itu ketika mau menambahkan member oleh admin, dan selalu muncul ini,

membersController.php

 <?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Role;
use App\User;
use Yajra\Datatables\Html\Builder;
use Yajra\Datatables\Facades\Datatables;
use App\Http\Requests\StoreMemberRequest;
use Illuminate\Support\Facades\Session;
use Illuminate\Support\Facades\Mail;

class MembersController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index(Request $request, Builder $htmlBuilder)
    {
        if ($request->ajax()) {
            $members = Role::where('name' , 'member')->first()->users;
            return Datatables::of($members)
            ->addColumn('action', function($member){
                return view('datatable._action', [
                    'model'     => $member,
                    'form_url'  => route('members.destroy', $member->id),
                    'edit_url'  => route('members.edit', $member->id),
                    'confirm_message' => 'Yakin mau menghapus ' .$member->name . '?'
                ]);
            })->make(true);
        }

        $html = $htmlBuilder
        ->addColumn(['data' => 'name', 'name'=>'name', 'title'=>'Nama'])
        ->addColumn(['data' => 'email', 'name'=>'email', 'title'=>'Email'])
        ->addColumn(['data' => 'action', 'name'=>'action', 'title'=>'','orderable'=>false,'searchable'=>false]);

        return view('members.index', compact('html'));
    }

    public function create()
    {
        return view('members.create');
    }

    public function store(StoreMemberRequest $request)
    {
        $password = str_random(6);
        $data = $request->all();
        $data['password'] = bcrypt($password);
        // bypass verifikasi
        $data['is_verified'] = 1;

        $member = User::create($data);

        // set role
        $memberRole = Role::where('name', 'member')->first();
        $member->attachRole($memberRole);

        // kirim email
        Mail::send('auth.emails.invite', compact('member', 'password'), function ($m) use ($member) {
            $m->to($member->email, $member->name)->subject('Anda telah didaftarkan di Larapus!');
        });

        Session::flash("flash_notification", [
            "level"   => "success",
            "message" => "Berhasil menyimpan member dengan email " .
            "<strong>" . $data['email'] . "</strong>" .
            " dan password <strong>" . $password . "</strong>."
        ]);

        return redirect()->route('members.index');
    }

    /**
     * Display the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function show($id)
    {
        //
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function edit($id)
    {
        //
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, $id)
    {
        //
    }

    /**
     * Remove the specified resource from storage.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function destroy($id)
    {
        //
    }
}

storeMemberRequest.php

 <?php

namespace App\Http\Requests;

use Illuminate\Foundation\Http\FormRequest;

class StoreMemberRequest extends FormRequest
{

    public function authorize()
    {
        return true;
    }

    public function rules()
    {
        return [
            'name'  => 'required|max:255',
            'email' => 'required|email|max:255|unique:users',
        ];
    }
}

invite.blade.php

	<p>
    Halo {{ $member->name }}.
</p>
<p>
    Admin kami telah mendaftarkan email Anda ({{ $member->email }}) ke Aswapus. Untuk login, silahkan kunjungi <a href="{{ $login = url('login') }}">{{ $login }}</a>. Login dengan email Anda dan password <strong>{{ $password }}</strong>.
</p
>

<p>
    Jika Anda ingin mengubah password, silahkan kunjungi <a href="{{ $reset = url('password/reset') }}">{{ $reset }}</a> dan masukan email Anda.
</p>