Here's a screenshot that might explain the situation better:

Is $user coming from controller.

Yes, $user is coming from the controller:

$user = User::find(3962);

$email = ProductEmail::find(1);

return new MarkdownTest($user, $email);

And here's MarkdownTest:

class MarkdownTest extends Mailable
{
    use Queueable, SerializesModels;

    public $user;

    public $email;

    public function __construct(User $user, ProductEmail $email)
    {
      $this->user = $user;

      $this->email = $email;
    }

    public function build()
    {
        return $this->markdown('emails.product.test');
    }
}

You are testing, but does the mail work for real? You never said test in original post.

If I send the mail through my SMTP server, I get exactly the same results as when previewing the mailable in my browser.

Everything in the mail is fine, except the curly braces aren't being processed.

Send data as object or array at Loop through fields like you would do a normal View just displaying data.

Thanks for your help with this, @jlrdw. Unfortunately, I don't understand what you mean.

As I've continued testing this issue, I've discovered that it's easy to duplicate in any view (not just mailers).

I created a view with nothing in it except the following:

Hello, {{ $user->name }}
{!! $email->body !!}

That generates the following output:

Hello, Justin (which is correct)
{{ $user->name }} (which is not correct—it's just echoing the contents of the db)

The contents of $email->body in the db:

It's important that I can store variables in the database. I want to build a CMS (of sorts) that lets people create email campaigns. Those campaigns should allow variables.

But it appears that Laravel can't "double process" variables. In other words, it can retrieve the contents of my database field, but it can't then process the variables in that field.

There has to be some way around this, but I'm at a loss.

I now realize that what I'm trying to do is essentially impossible. I'm trying to parse data after it's already been parsed. :D

Thanks again for your help, @jlrdw .