Expected response code "250/251/252" but got code "451", with message "451 Temporary local problem - please try later"

Question

I am new in Laravel development. I am sending an email to agencies which is approved and email is not null and if agencies email is null then get customer email for send email, But I got this error https://flareapp.io/share/DPygyxQ5#F57

I have tried to figure out where is the issue using echo pre in every steps. I am using smtp for sending email.

If you think that is there issue in smtp so if user register itself then email is successfully sent to user.

Here is code

// Get agency details
    $agencies = Agency::where('status', 2)->get();
    $property = Property::where('property_id', $id)->first();

    if($agencies->isNotEmpty())
    {
        foreach($agencies as $agency)
        {
            if($agency->email != null)
            {
                $agency_name    = $agency->name;
                $agency_email   = $agency->email;
                $property_slug  = $property->slug;
                $property_link  = route('property.detail', $property_slug);


                Mail::send('emails.user.agency.mail_to_agency_after_property_approve',
                [
                    'agency_email'          =>  $agency_email,
                    'agency_name'           =>  $agency_name,
                    'property'              =>  $property,
                    'property_link'         =>  $property_link,
                ],
                function($message) use ($agency_email)
                {
                    $message->to($agency_email);
                    $message->subject('Fresh Property Listing Update');
                });
            }
            else
            {
                $customer = Customer::select('customer_id', 'first_name', 'last_name', 'customer_email')->where('customer_id', $agency->customer_id)->first();

                $agency_name    = $customer->first_name.' '.$customer->last_name;
                $agency_email   = $customer->customer_email;
                $property_slug  = $property->slug;
                $property_link  = route('property.detail', $property_slug);

                Mail::send('emails.user.agency.mail_to_agency_after_property_approve',
                [
                    'agency_email'          =>  $agency_email,
                    'agency_name'           =>  $agency_name,
                    'property'              =>  $property,
                    'property_link'         =>  $property_link,
                ],
                function($message) use ($agency_email)
                {
                    $message->to($agency_email);
                    $message->subject('Fresh Property Listing Update');
                });
            }
            
        }
    }