src/Viserio/Component/Mail/Mailer.php
protected function callMessageBuilder($callback, MessageContract $message)
    {
        if ($callback instanceof Closure) {
            return $callback($message);
        }

        if ($this->container !== null) {
            return $this->getInvoker()->call($callback)->mail($message);
        }

        throw new InvalidArgumentException('Callback is not valid.');
    }
protected function callMessageBuilder($callback, MessageContract $message)
    {
        if ($callback instanceof Closure) {
            return $callback($message);
        }

        if ($this->container !== null) {
            return $this->getInvoker()->call($callback)->mail($message);
        }

        throw new InvalidArgumentException('Callback is not valid.');
    }
Call the provided message builder.

@param null|\Closure|string                     $callback
@param \Viserio\Component\Contract\Mail\Message $message

@throws \InvalidArgumentException

@return mixed