diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index e45e2e6..ae38975 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -6,7 +6,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest]
-        php-versions: ['8.1', '8.0']
+        php-versions: ['8.2', '8.1', '8.0']
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v1
@@ -16,7 +16,6 @@ jobs:
           php-version: ${{ matrix.php-versions }}
           extensions: dom, libxml, mbstring, intl, xml, fileinfo, zip
           coverage: xdebug
-          tools: prestissimo
       - name: Get composer cache directory
         id: composer-cache
         run: echo "::set-output name=dir::$(composer config cache-files-dir)"
@@ -24,7 +23,7 @@ jobs:
         uses: actions/cache@v1
         with:
           path: ${{ steps.composer-cache.outputs.dir }}
-          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}
           restore-keys: ${{ runner.os }}-composer-
       - name: Install Composer dependencies
         run: composer install --no-ansi --no-interaction --no-progress --optimize-autoloader
@@ -32,6 +31,8 @@ jobs:
         run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
       - name: Test with phpunit
         run: vendor/bin/phpunit --coverage-text
+      - name: Check for vulnerabilities
+        run: composer security-checker
   composer-normalize:
     runs-on: ubuntu-latest
     steps:
diff --git a/README.md b/README.md
index bd9aecd..cb914a7 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ Laravel Symfony Mailer CSS Inliner
 Most email clients won't render CSS (on a `<link>` or a `<style>`). The solution is inline your CSS directly on the HTML. Doing this by hand easily turns into unmantainable templates.
 The goal of this package is to automate the process of inlining that CSS before sending the emails.
 
-## Instalation and compatability
+## Installation and compatability
 
 Requires PHP 8.1 and Laravel 9.0 or higher.
 
diff --git a/composer.json b/composer.json
index 0d0d54e..6d95779 100644
--- a/composer.json
+++ b/composer.json
@@ -23,6 +23,7 @@
         "tijsverkoyen/css-to-inline-styles": "~2.2"
     },
     "require-dev": {
+        "enlightn/security-checker": "^1.10",
         "phpunit/phpunit": "^9.0 || ^10",
         "symfony/mailer": "^6.0"
     },
@@ -45,5 +46,11 @@
         "psr-4": {
             "Tests\\": "tests/"
         }
+    },
+    "scripts": {
+        "security-checker": "security-checker security:check"
+    },
+    "scripts-descriptions": {
+        "security-checker": "Checks if your application uses dependencies with known security vulnerabilities."
     }
 }
diff --git a/src/CssInlinerPlugin.php b/src/CssInlinerPlugin.php
index 0ed1f18..5f634a5 100644
--- a/src/CssInlinerPlugin.php
+++ b/src/CssInlinerPlugin.php
@@ -3,14 +3,15 @@
 namespace ajohnson6494\LaravelSymfonyMailerCssInliner;
 
 use DOMDocument;
-use Symfony\Component\Mime\Message;
-use Symfony\Component\Mime\Part\TextPart;
 use Illuminate\Mail\Events\MessageSending;
-use Symfony\Component\Mime\Part\AbstractPart;
+use Symfony\Component\Mime\Email;
 use Symfony\Component\Mailer\Event\MessageEvent;
+use Symfony\Component\Mime\Part\AbstractPart;
+use Symfony\Component\Mime\Part\AbstractMultipartPart;
+use Symfony\Component\Mime\Part\Multipart\AlternativePart;
 use Symfony\Component\Mime\Part\Multipart\MixedPart;
+use Symfony\Component\Mime\Part\TextPart;
 use TijsVerkoyen\CssToInlineStyles\CssToInlineStyles;
-use Symfony\Component\Mime\Part\Multipart\AlternativePart;
 
 class CssInlinerPlugin
 {
@@ -29,28 +30,37 @@ public function handle(MessageSending $event): void
     {
         $message = $event->message;
 
-        if (!$message instanceof Message) {
+        if (!$message instanceof Email) {
             return;
         }
 
-        $this->handleSymfonyMessage($message);
+        $this->handleSymfonyEmail($message);
     }
 
     public function handleSymfonyEvent(MessageEvent $event): void
     {
         $message = $event->getMessage();
 
-        if (!$message instanceof Message) {
+        if (!$message instanceof Email) {
             return;
         }
 
-        $this->handleSymfonyMessage($message);
+        $this->handleSymfonyEmail($message);
     }
 
     private function processPart(AbstractPart $part): AbstractPart
     {
         if ($part instanceof TextPart && $part->getMediaType() === 'text' && $part->getMediaSubtype() === 'html') {
             return $this->processHtmlTextPart($part);
+        } else if ($part instanceof AbstractMultipartPart) {
+            $part_class = get_class($part);
+            $parts = [];
+
+            foreach ($part->getParts() as $childPart) {
+                $parts[] = $this->processPart($childPart);
+            }
+
+            return new $part_class(...$parts);
         }
 
         return $part;
@@ -76,7 +86,7 @@ private function processHtmlTextPart(TextPart $part): TextPart
         return new TextPart($bodyString, $part->getPreparedHeaders()->getHeaderParameter('Content-Type', 'charset') ?: 'utf-8', 'html');
     }
 
-    private function handleSymfonyMessage(Message $message): void
+    private function handleSymfonyEmail(Email $message): void
     {
         $body = $message->getBody();
 
@@ -87,26 +97,13 @@ private function handleSymfonyMessage(Message $message): void
         if ($body instanceof TextPart) {
             $message->setBody($this->processPart($body));
         } elseif ($body instanceof AlternativePart || $body instanceof MixedPart) {
-          $originalParts = $body->getParts();
-          $allParts = [];
-
-          foreach($originalParts as $part) {
-            if ($part->getMediaType() === "multipart") {
-              /** @var \Symfony\Component\Mime\Part\Multipart $part */
-              foreach ($part->getParts() as $p) {
-                $allParts[] = $p;
-              }
-            } else {
-              $allParts[] = $part;
-            }
-          }
-
-          $message->setBody(new AlternativePart(
-            ...array_map(
-                fn (AbstractPart $part) => $this->processPart($part),
-                $allParts
-            )
-          ));
+            $part_type = get_class($body);
+            $message->setBody(new $part_type(
+                ...array_map(
+                    fn (AbstractPart $part) => $this->processPart($part),
+                    $body->getParts()
+                )
+            ));
         }
     }
 
diff --git a/tests/CssInlinerPluginTest.php b/tests/CssInlinerPluginTest.php
index 57a6fcb..10055dd 100644
--- a/tests/CssInlinerPluginTest.php
+++ b/tests/CssInlinerPluginTest.php
@@ -2,20 +2,20 @@
 
 namespace Tests;
 
-use Illuminate\Support\Collection;
-use PHPUnit\Framework\TestCase;
 use RuntimeException;
-use ajohnson6494\LaravelSymfonyMailerCssInliner\CssInlinerPlugin;
-use Symfony\Component\EventDispatcher\EventDispatcher;
-use Symfony\Component\Mailer\Event\MessageEvent;
-use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mime\Email;
+use Illuminate\Support\Collection;
 use Symfony\Component\Mailer\Mailer;
 use Symfony\Component\Mailer\Transport;
-use Symfony\Component\Mime\Email;
-use Symfony\Component\Mime\Part\AbstractMultipartPart;
-use Symfony\Component\Mime\Part\Multipart\AlternativePart;
-use Symfony\Component\Mime\Part\Multipart\MixedPart;
 use Symfony\Component\Mime\Part\TextPart;
+use Symfony\Component\Mime\Part\AbstractPart;
+use Symfony\Component\Mailer\Event\MessageEvent;
+use Symfony\Component\Mime\Exception\LogicException;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+use Symfony\Component\Mime\Part\AbstractMultipartPart;
+use ajohnson6494\LaravelSymfonyMailerCssInliner\CssInlinerPlugin;
+use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
 
 class CssInlinerPluginTest extends TestCase
 {
@@ -63,11 +63,16 @@ public function test_it_should_convert_html_body(): void
 
     public function test_it_should_convert_html_body_with_attachment(): void
     {
-        $message = $this->fakeSendMessageWithAttachmentUsingInlinePlugin(
-            (new Email)->html($this->stubs['original-html'])
+        $originalMessage = $this->createMessageToSend(
+            (new Email)->html($this->stubs['original-html']),
+            __DIR__ . '/stubs/original-html.stub'
         );
 
+        $message = $this->fakeSendMessageUsingInlinePlugin($originalMessage);
+
         $this->assertBodyMatchesStub($message, 'converted-html');
+        $this->assertSameMessageStructure($originalMessage, $message);
+        $this->assertAttachmentsAreIdentical($originalMessage, $message);
     }
 
     public function test_it_should_convert_html_body_with_given_css(): void
@@ -80,14 +85,21 @@ public function test_it_should_convert_html_body_with_given_css(): void
         $this->assertBodyMatchesStub($message, 'converted-html-with-css');
     }
 
-    public function test_it_should_convert_html_body_with_given_css_with_attachment(): void
+    public function test_it_should_convert_html_body_with_given_css_and_attachment(): void
     {
-        $message = $this->fakeSendMessageWithAttachmentUsingInlinePlugin(
+        $originalMessage = $this->createMessageToSend(
             (new Email)->html($this->stubs['original-html-with-css']),
+            __DIR__ . '/stubs/original-html.stub'
+        );
+
+        $message = $this->fakeSendMessageUsingInlinePlugin(
+            $originalMessage,
             [__DIR__ . '/css/test.css']
         );
 
         $this->assertBodyMatchesStub($message, 'converted-html-with-css');
+        $this->assertSameMessageStructure($originalMessage, $message);
+        $this->assertAttachmentsAreIdentical($originalMessage, $message);
     }
 
     public function test_it_should_convert_html_body_and_text_parts(): void
@@ -104,14 +116,17 @@ public function test_it_should_convert_html_body_and_text_parts(): void
 
     public function test_it_should_convert_html_body_and_text_parts_with_attachment(): void
     {
-        $message = $this->fakeSendMessageWithAttachmentUsingInlinePlugin(
-            (new Email)
-                ->html($this->stubs['original-html'])
-                ->text($this->stubs['plain-text'])
+        $originalMessage = $this->createMessageToSend(
+            (new Email)->html($this->stubs['original-html'])->text($this->stubs['plain-text']),
+            __DIR__ . '/stubs/original-html.stub'
         );
 
+        $message = $this->fakeSendMessageUsingInlinePlugin($originalMessage);
+
         $this->assertBodyMatchesStub($message, 'converted-html');
         $this->assertBodyMatchesStub($message, 'plain-text', 'plain');
+        $this->assertSameMessageStructure($originalMessage, $message);
+        $this->assertAttachmentsAreIdentical($originalMessage, $message);
     }
 
     public function test_it_should_leave_plain_text_unmodified(): void
@@ -120,16 +135,21 @@ public function test_it_should_leave_plain_text_unmodified(): void
             (new Email)->text($this->stubs['plain-text'])
         );
 
-        $this->assertBodyMatchesStub($message, 'plain-text');
+        $this->assertBodyMatchesStub($message, 'plain-text', 'plain');
     }
 
     public function test_it_should_leave_plain_text_unmodified_with_attachment(): void
     {
-        $message = $this->fakeSendMessageWithAttachmentUsingInlinePlugin(
+        $originalMessage = $this->createMessageToSend(
             (new Email)->text($this->stubs['plain-text']),
+            __DIR__ . '/stubs/original-html.stub'
         );
 
+        $message = $this->fakeSendMessageUsingInlinePlugin($originalMessage);
+
         $this->assertBodyMatchesStub($message, 'plain-text', 'plain');
+        $this->assertSameMessageStructure($originalMessage, $message);
+        $this->assertAttachmentsAreIdentical($originalMessage, $message);
     }
 
     public function test_it_should_convert_html_body_as_a_part(): void
@@ -143,11 +163,15 @@ public function test_it_should_convert_html_body_as_a_part(): void
 
     public function test_it_should_convert_html_body_as_a_part_with_attachment(): void
     {
-        $message = $this->fakeSendMessageWithAttachmentUsingInlinePlugin(
-            (new Email)->html($this->stubs['original-html'])
+        $originalMessage = $this->createMessageToSend(
+            (new Email)->html($this->stubs['original-html']),
+            __DIR__ . '/stubs/original-html.stub'
         );
+        $message = $this->fakeSendMessageUsingInlinePlugin($originalMessage);
 
         $this->assertBodyMatchesStub($message, 'converted-html');
+        $this->assertSameMessageStructure($originalMessage, $message);
+        $this->assertAttachmentsAreIdentical($originalMessage, $message);
     }
 
     public function test_it_should_convert_html_body_with_link_css(): void
@@ -159,13 +183,18 @@ public function test_it_should_convert_html_body_with_link_css(): void
         $this->assertBodyMatchesStub($message, 'converted-html-with-css');
     }
 
-    public function test_it_should_convert_html_body_with_link_css_with_attachment(): void
+    public function test_it_should_convert_html_body_with_link_css_and_attachment(): void
     {
-        $message = $this->fakeSendMessageWithAttachmentUsingInlinePlugin(
-            (new Email)->html($this->stubs['original-html-with-link-css'])
+        $originalMessage = $this->createMessageToSend(
+            (new Email)->html($this->stubs['original-html-with-link-css']),
+            __DIR__ . '/stubs/original-html.stub'
         );
 
+        $message = $this->fakeSendMessageUsingInlinePlugin($originalMessage);
+
         $this->assertBodyMatchesStub($message, 'converted-html-with-css');
+        $this->assertSameMessageStructure($originalMessage, $message);
+        $this->assertAttachmentsAreIdentical($originalMessage, $message);
     }
 
     public function test_it_should_convert_html_body_with_links_css(): void
@@ -177,78 +206,106 @@ public function test_it_should_convert_html_body_with_links_css(): void
         $this->assertBodyMatchesStub($message, 'converted-html-with-links-css');
     }
 
-    public function test_it_should_convert_html_body_with_links_css_with_attachment(): void
+    public function test_it_should_convert_html_body_with_links_css_and_attachment(): void
     {
-        $message = $this->fakeSendMessageWithAttachmentUsingInlinePlugin(
-            (new Email)->html($this->stubs['original-html-with-links-css'])
+        $originalMessage = $this->createMEssageToSend(
+            (new Email)->html($this->stubs['original-html-with-links-css']),
+            __DIR__ . '/stubs/original-html.stub'
         );
+        $message = $this->fakeSendMessageUsingInlinePlugin($originalMessage);
 
         $this->assertBodyMatchesStub($message, 'converted-html-with-links-css');
+        $this->assertSameMessageStructure($originalMessage, $message);
+        $this->assertAttachmentsAreIdentical($originalMessage, $message);
     }
 
-    private function assertBodyMatchesStub(object $message, string $stub, string $mediaSubType = 'html'): void
+    private function assertBodyMatchesStub(Email $message, string $stub, string $mediaSubType = 'html'): void
     {
-        $this->assertInstanceOf(Email::class, $message);
-
         $body = $message->getBody();
 
-        if ($body instanceof TextPart) {
-            $actual = $body->getBody();
-        } elseif ($body instanceof AlternativePart || $body instanceof MixedPart) {
-            $actual = (new Collection($body->getParts()))->first(
-                static fn ($part) => $part instanceof TextPart && $part->getMediaType() === 'text' && $part->getMediaSubtype() === $mediaSubType
-            )->getBody();
-        } else {
+        if (! $body instanceof AbstractPart) {
             throw new RuntimeException('Unknown message body type');
         }
 
+        $actual = $this->getTextFromPart($body, $mediaSubType);
+
+        if (is_null($actual)) {
+            throw new RuntimeException("No text found in body with media subtype '$mediaSubType'" );
+        }
+
         $this->assertEquals($this->stubs[$stub], $this->cleanupHtmlStringForComparison($actual));
     }
 
-    private function cleanupHtmlStringForComparison(string $string): string
+    private function assertSameMessageStructure(Email $expected, Email $actual)
     {
-        // Strip out all newlines and trim newlines from the start and end
-        $string = str_replace("\n", '', trim($string));
+        $expected_structure = $this->getMessagePartStructure($expected->getBody());
+        $actual_structure = $this->getMessagePartStructure($actual->getBody());
 
-        // Strip out any whitespace between HTML tags
-        return preg_replace('/(>)\s+(<\/?[a-z]+)/', '$1$2', $string);
+        $this->assertEquals($expected_structure, $actual_structure);
     }
 
-    private function fakeSendMessageUsingInlinePlugin(Email $message, array $inlineCssFiles = []): Email
+    private function assertAttachmentsAreIdentical(Email $expected, Email $actual)
     {
-        $processedMessage = null;
+        $expected_attachments = $expected->getAttachments();
+        $actual_attachments = $actual->getAttachments();
 
-        $dispatcher = new EventDispatcher;
-        $dispatcher->addListener(MessageEvent::class, static function (MessageEvent $event) use ($inlineCssFiles, &$processedMessage) {
-            $handler = new CssInlinerPlugin($inlineCssFiles);
+        $this->assertGreaterThan(0, count($expected_attachments));
+        $this->assertSameSize($expected_attachments, $actual_attachments);
 
-            $handler->handleSymfonyEvent($event);
+        for ($i = 0; $i < count($expected_attachments); $i++) {
+            $this->assertEquals($expected_attachments[$i]->getBody(), $actual_attachments[$i]->getBody());
+        }
+    }
 
-            $processedMessage = $event->getMessage();
-        });
+    private function getMessagePartStructure(AbstractPart $part): array|string
+    {
+        $structure = [];
 
-        $mailer = new Mailer(
-            Transport::fromDsn('null://default', $dispatcher)
-        );
+        $partClass = get_class($part);
 
-        try {
-            $mailer->send(
-                $message->to('test2@example.com')
-                        ->from('test@example.com')
-                        ->subject('Test')
-            );
-        } catch (TransportExceptionInterface) {
-            // We are not really expecting anything to happen here considering it's a `NullTransport` we are using :)
+        if (! $part instanceof AbstractMultipartPart) {
+            $structure[] = $partClass;
+        } else {
+            $structure[$partClass] = [];
+            foreach ($part->getParts() as $childPart) {
+                $structure[$partClass][] = $this->getMessagePartStructure($childPart);
+            }
         }
 
-        if (!$processedMessage instanceof Email) {
-            throw new RuntimeException('No email was processed!');
+        if (count($structure, COUNT_RECURSIVE) === 1) {
+            $structure = $structure[0];
         }
 
-        return $processedMessage;
+        return $structure;
+    }
+
+    private function cleanupHtmlStringForComparison(string $string): string
+    {
+        // Strip out all newlines and trim newlines from the start and end
+        $string = str_replace("\n", '', trim($string));
+
+        // Strip out any whitespace between HTML tags
+        return preg_replace('/(>)\s+(<\/?[a-z]+)/', '$1$2', $string);
+    }
+
+    private function getTextFromPart(AbstractPart $part, string $mediaSubType = 'html'): ?string
+    {
+        if ($part instanceof TextPart && $part->getMediaType() === 'text' && $part->getMediaSubtype() === $mediaSubType) {
+            return $part->getBody();
+        } elseif ($part instanceof AbstractMultipartPart) {
+            foreach ($part->getParts() as $childPart) {
+                $text = $this->getTextFromPart($childPart, $mediaSubType);
+
+                if (! is_null($text)) {
+                    return $text;
+                }
+            }
+        }
+
+        return null;
     }
 
-    private function fakeSendMessageWithAttachmentUsingInlinePlugin(Email $message, array $inlineCssFiles = []): Email
+    private function fakeSendMessageUsingInlinePlugin(Email $message, array $inlineCssFiles = []): Email
     {
         $processedMessage = null;
 
@@ -265,13 +322,15 @@ private function fakeSendMessageWithAttachmentUsingInlinePlugin(Email $message,
             Transport::fromDsn('null://default', $dispatcher)
         );
 
+        // Check if the message is valid (has to, cc and bcc set). If not, we create a valid message.
         try {
-            $mailer->send(
-                $message->to('test2@example.com')
-                        ->from('test@example.com')
-                        ->subject('Test')
-                        ->attachFromPath(__DIR__ . "/stubs/attachment.txt")
-            );
+            $message->ensureValidity();
+        } catch (LogicException) {
+            $message = $this->createMessageToSend($message);
+        }
+
+        try {
+            $mailer->send($message);
         } catch (TransportExceptionInterface) {
             // We are not really expecting anything to happen here considering it's a `NullTransport` we are using :)
         }
@@ -282,4 +341,17 @@ private function fakeSendMessageWithAttachmentUsingInlinePlugin(Email $message,
 
         return $processedMessage;
     }
+
+    private function createMessageToSend(Email $message, string $attachmentPath = null): Email
+    {
+        $message = $message->to('test2@example.com')
+                    ->from('test@example.com')
+                    ->subject('Test');
+
+        if (! is_null($attachmentPath)) {
+            $message = $message->attachFromPath($attachmentPath);
+        }
+
+        return $message;
+    }
 }