invoiceninja/app/Mail/TemplateEmail.php

<?php
namespace App\Mail;

use App\Models\Client;
use App\Models\User;
use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;

class TemplateEmail extends Mailable
{
    use Queueable, SerializesModels;

    private $build_email; 

    private $user; //the user the email will be sent from
    
    private $client;
    
    private $footer;

    public function __construct($build_email, User $user, Client $client)
    {
    
        $this->build_email = $build_email;

        $this->user = $user; //this is inappropriate here, need to refactor 'user' in this context the 'user' could also be the 'system'
        
        $this->client = $client;
    
    }

    /**
     * Build the message.
     *
     * @return $this
     */
    public function build()
    {
        /*Alter Run Time Mailer configuration (driver etc etc) to regenerate the Mailer Singleton*/

        //if using a system level template
        $template_name = 'email.template.' . $this->build_email->getTemplate();

        $settings = $this->client->getMergedSettings();

        $company = $this->client->company;

        $message = $this->from($this->user->email,$this->user->present()->name())//todo this needs to be fixed to handle the hosted version
            ->subject($this->build_email->getSubject())
            ->text('email.template.plain', [
                'body' => $this->build_email->getBody(), 
                'footer' => $this->build_email->getFooter()
            ])
            ->view($template_name, [
                'body' => $this->build_email->getBody(),
                'footer' => $this->build_email->getFooter(),
                'title' => $this->build_email->getSubject(),
                'settings' => $settings,
                'company' => $company
            ]);

         //conditionally attach files
         if($settings->pdf_email_attachment !== false && !empty($this->build_email->getAttachments())){

             foreach($this->build_email->getAttachments() as $file)
                 $message->attach($file);
         }

         return $message;
    }
}