Laravel 5.1 Mail :: raw工作但Mail :: send没有

I am using Laravel 5.1 email with Amazon SES.

If I use:

Mail::send('mymail', function ($m) use ($user)  or Mail::send('mymail', $data, function ($m) use ($user)  

It doesn't work. I get a 500 error.

However if I use:

Mail::raw('Hello this is a test message', function ($m) use ($user)

It works fine.

Any thoughts what could be causing this?