Duplicate entry in table in laravel

Hi i am facing an issue through loop i am sending email but it save record two time or 4times also in table. i also add check if rec is null then it do an entry here it is my code

DB::table('sendportal_subscribers')->where('unsubscribed_at',NULL)->orderBy('id')->chunk(300, function ($subscribers) use ($template_campaign,$campaign) {
                    foreach ($subscribers as $subscriber) {
                        
                        $check = DB::table('sendportal_messages')->where(['source_id'=>$campaign->id,'subscriber_id' => $subscriber->id,'recipient_email'=>$subscriber->email])->first();
                        if (is_null($check)) {

                           
                           //save entry
                           $data = [

                               'hash'=> Hash::make($subscriber->email),
                               'workspace_id'=>1,
                               'subscriber_id' => $subscriber->id,
                               'source_type'=>'Sendportal\Base\Models\Campaign',
                               'source_id' => $campaign->id,
                               'recipient_email'=> $subscriber->email,
                               'subject'=> $campaign->name,
                               'from_name'=> $campaign->from_name,
                               'from_email'=>$campaign->from_email,
                               'open_count'=>0,
                               'click_count'=>0,
                               'sent_at'=>now(),
                               'created_at'=>now()
                           ];    
                           DB::table('sendportal_messages')->insert($data);
						 //send mail 
                           sendEmailCampaignJob::dispatch($subscriber->email ,$campaign->subject);
				}

here it is table data

it store 4 times record in table for same entry Thanks for any help