diff --git a/src/Knp/UniMail/AttachmentFactory/RemoteAttachmentFactory.php b/src/Knp/UniMail/AttachmentFactory/RemoteAttachmentFactory.php
index ebbd933..f9b95c1 100644
--- a/src/Knp/UniMail/AttachmentFactory/RemoteAttachmentFactory.php
+++ b/src/Knp/UniMail/AttachmentFactory/RemoteAttachmentFactory.php
@@ -22,7 +22,7 @@ public function supports($content)
             return false;
         }
 
-        return false === strpos($headers[0],'404');
+        return false === strpos($headers[0], '404');
     }
 
     /**
diff --git a/src/Knp/UniMail/Cid/Collection.php b/src/Knp/UniMail/Cid/Collection.php
new file mode 100644
index 0000000..ba7f013
--- /dev/null
+++ b/src/Knp/UniMail/Cid/Collection.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace Knp\UniMail\Cid;
+
+use Swift_Mime_Attachment;
+
+class Collection implements \IteratorAggregate
+{
+    /**
+     * @var Swift_Mime_Attachment[]
+     */
+    private $cids;
+
+    /**
+     * @param Swift_Mime_Attachment[] $cids
+     */
+    public function __construct($cids = [])
+    {
+        $this->cids = $cids;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getIterator()
+    {
+        return new \ArrayIterator($this->cids);
+    }
+
+    /**
+     * @return Swift_Mime_Attachment[]
+     */
+    public function all()
+    {
+        return $this->cids;
+    }
+
+    /**
+     * @param Swift_Mime_Attachment $cid
+     *
+     * @return Collection
+     */
+    public function add(Swift_Mime_Attachment $cid)
+    {
+        $this->cids[$cid->getId()] = $cid;
+
+        return $this;
+    }
+
+    /**
+     * @return Collection
+     */
+    public function clear()
+    {
+        $this->cids = [];
+
+        return $this;
+    }
+}
diff --git a/src/Knp/UniMail/Cid/Resolver.php b/src/Knp/UniMail/Cid/Resolver.php
new file mode 100644
index 0000000..ce3a604
--- /dev/null
+++ b/src/Knp/UniMail/Cid/Resolver.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace Knp\UniMail\Cid;
+
+interface Resolver
+{
+    /**
+     * @param string $string
+     *
+     * @return Swift_EmbeddedFile|null
+     */
+    public function createFromString($string);
+}
diff --git a/src/Knp/UniMail/Cid/Resolver/LocalFile.php b/src/Knp/UniMail/Cid/Resolver/LocalFile.php
new file mode 100644
index 0000000..c88a805
--- /dev/null
+++ b/src/Knp/UniMail/Cid/Resolver/LocalFile.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Knp\UniMail\Cid\Resolver;
+
+use Knp\UniMail\Cid\Resolver;
+use Swift_EmbeddedFile;
+
+class LocalFile implements Resolver
+{
+    /**
+     * @var string
+     */
+    private $directory;
+
+    /**
+     * @param string $directory
+     */
+    public function __construct($directory)
+    {
+        $this->directory = $directory;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function createFromString($string)
+    {
+        $string = str_replace('/', DIRECTORY_SEPARATOR, $string);
+
+        if (false === file_exists($string)) {
+            return;
+        }
+
+        return Swift_EmbeddedFile::fromPath(sprintf('%s%s%s', $this->directory, DIRECTORY_SEPARATOR, $string));
+    }
+}
diff --git a/src/Knp/UniMail/Cid/Resolver/RemoteFile.php b/src/Knp/UniMail/Cid/Resolver/RemoteFile.php
new file mode 100644
index 0000000..d1325d3
--- /dev/null
+++ b/src/Knp/UniMail/Cid/Resolver/RemoteFile.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace Knp\UniMail\Cid\Resolver;
+
+use Knp\UniMail\Cid\Resolver;
+use Swift_EmbeddedFile;
+
+class RemoteFile implements Resolver
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function createFromString($string)
+    {
+        $headers = @get_headers($string);
+
+        if (false === $headers) {
+            return;
+        }
+
+        if (false !== strpos($headers[0], '404')) {
+            return;
+        }
+
+        return Swift_EmbeddedFile::fromPath($string);
+    }
+}
diff --git a/src/Knp/UniMail/EventListener/AttachmentResolver.php b/src/Knp/UniMail/EventListener/AttachmentResolver.php
index b1a57ca..d47b5fb 100644
--- a/src/Knp/UniMail/EventListener/AttachmentResolver.php
+++ b/src/Knp/UniMail/EventListener/AttachmentResolver.php
@@ -18,7 +18,7 @@ public function __construct(AttachmentFactory $factory)
     public static function getSubscribedEvents()
     {
         return [
-            MailerEvents::PRE_SEND => array('beforeSend', -2)
+            MailerEvents::PRE_SEND => array('beforeSend', -2),
         ];
     }
 
diff --git a/src/Knp/UniMail/EventListener/CidAttachmentMerger.php b/src/Knp/UniMail/EventListener/CidAttachmentMerger.php
index bbb2db9..2c0af1a 100644
--- a/src/Knp/UniMail/EventListener/CidAttachmentMerger.php
+++ b/src/Knp/UniMail/EventListener/CidAttachmentMerger.php
@@ -2,7 +2,7 @@
 
 namespace Knp\UniMail\EventListener;
 
-use Doctrine\Common\Collections\ArrayCollection;
+use Knp\UniMail\Cid\Collection;
 use Knp\UniMail\MailerEvent;
 use Knp\UniMail\MailerEvents;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
@@ -11,7 +11,7 @@ class CidAttachmentMerger implements EventSubscriberInterface
 {
     private $cids;
 
-    public function __construct(ArrayCollection $cids)
+    public function __construct(Collection $cids)
     {
         $this->cids = $cids;
     }
@@ -19,7 +19,7 @@ public function __construct(ArrayCollection $cids)
     public static function getSubscribedEvents()
     {
         return [
-            MailerEvents::PRE_SEND => array('beforeSend', -3)
+            MailerEvents::PRE_SEND => array('beforeSend', -3),
         ];
     }
 
@@ -28,7 +28,7 @@ public function beforeSend(MailerEvent $event)
         $mail        = $event->getMail();
         $attachments = $mail->getAttachments();
         $attachments = array_merge(
-            $this->cids->toArray(),
+            $this->cids->all(),
             $attachments
         );
 
diff --git a/src/Knp/UniMail/EventListener/TwigRenderer.php b/src/Knp/UniMail/EventListener/TwigRenderer.php
index f76dcbb..a2ed790 100644
--- a/src/Knp/UniMail/EventListener/TwigRenderer.php
+++ b/src/Knp/UniMail/EventListener/TwigRenderer.php
@@ -21,7 +21,7 @@ public function __construct(Twig_Environment $twig)
     public static function getSubscribedEvents()
     {
         return [
-            MailerEvents::PRE_SEND => array('beforeSend', -2)
+            MailerEvents::PRE_SEND => array('beforeSend', -2),
         ];
     }
 
diff --git a/src/Knp/UniMail/MailFactory/StrategyMailer/TwigMailFactory.php b/src/Knp/UniMail/MailFactory/StrategyMailer/TwigMailFactory.php
index 17dcfe0..daaa6c6 100644
--- a/src/Knp/UniMail/MailFactory/StrategyMailer/TwigMailFactory.php
+++ b/src/Knp/UniMail/MailFactory/StrategyMailer/TwigMailFactory.php
@@ -2,9 +2,9 @@
 
 namespace Knp\UniMail\MailFactory\StrategyMailer;
 
+use Knp\UniMail\Mail\TwigMail;
 use Knp\UniMail\MailFactory;
 use Knp\UniMail\MailFactory\StrategyMailer;
-use Knp\UniMail\Mail\TwigMail;
 use Symfony\Component\PropertyAccess\PropertyAccess;
 
 class TwigMailFactory implements StrategyMailer, MailFactory
diff --git a/src/Knp/UniMail/Mailer/SwiftMailer.php b/src/Knp/UniMail/Mailer/SwiftMailer.php
index a8c19d3..f863984 100644
--- a/src/Knp/UniMail/Mailer/SwiftMailer.php
+++ b/src/Knp/UniMail/Mailer/SwiftMailer.php
@@ -3,9 +3,9 @@
 namespace Knp\UniMail\Mailer;
 
 use Knp\UniMail\Mail;
-use Knp\UniMail\MailFactory;
 use Knp\UniMail\Mail\SwiftMail;
 use Knp\UniMail\Mailer;
+use Knp\UniMail\MailFactory;
 use Swift_Mailer;
 use Swift_Message;
 
diff --git a/src/Knp/UniMail/Mailer/TwigMailer.php b/src/Knp/UniMail/Mailer/TwigMailer.php
index 9999236..1e5f0a6 100644
--- a/src/Knp/UniMail/Mailer/TwigMailer.php
+++ b/src/Knp/UniMail/Mailer/TwigMailer.php
@@ -4,8 +4,8 @@
 
 use Doctrine\Common\Collections\ArrayCollection;
 use Knp\UniMail\Mail;
-use Knp\UniMail\MailFactory;
 use Knp\UniMail\Mailer as MailerInterface;
+use Knp\UniMail\MailFactory;
 use Swift_Mailer;
 use Swift_Message;
 use Twig_Environment;
diff --git a/src/Knp/UniMail/Resources/config/services.yml b/src/Knp/UniMail/Resources/config/services.yml
index c7556b0..5e4e872 100644
--- a/src/Knp/UniMail/Resources/config/services.yml
+++ b/src/Knp/UniMail/Resources/config/services.yml
@@ -18,13 +18,20 @@ services:
     knp_unimail.attachment_factory:
         alias: knp_unimail.attachment_factory.chain_attachment_factory
 
-    knp_unimail.collection.cids:
-        class: Doctrine\Common\Collections\ArrayCollection
+    knp_unimail.cid.collection:
+        class: Knp\UniMail\Cid\Collection
+
+    knp_unimail.event_listener.attachment_resolver:
+        class: Knp\UniMail\EventListener\AttachmentResolver
+        arguments:
+            - @knp_unimail.attachment_factory
+        tags:
+          - { name: kernel.event_subscriber }
 
     knp_unimail.event_listener.cid_attachment_merger:
         class: Knp\UniMail\EventListener\CidAttachmentMerger
         arguments:
-            - @knp_unimail.collection.cids
+            - @knp_unimail.cid.collection
         tags:
           - { name: kernel.event_subscriber }
 
@@ -35,13 +42,6 @@ services:
         tags:
           - { name: kernel.event_subscriber }
 
-    knp_unimail.event_listener.attachment_resolver:
-        class: Knp\UniMail\EventListener\AttachmentResolver
-        arguments:
-            - @knp_unimail.attachment_factory
-        tags:
-          - { name: kernel.event_subscriber }
-
     knp_unimail.mail_factory.configuration_aware_factory:
         class: Knp\UniMail\MailFactory\ConfigurationAwareFactory
         public: false
@@ -83,8 +83,17 @@ services:
     knp_unimail.twig.cid_extension:
         class: Knp\UniMail\Twig\CidExtension
         arguments:
-            - @knp_unimail.collection.cids
-            - %knp_unimail.attachments_directory%
+            - @knp_unimail.cid.collection
+            - [@knp_unimail.cid.resolver.local_file, @knp_unimail.cid.resolver.remove_file]
         tags:
             - { name: twig.extension }
 
+    knp_unimail.cid.resolver.local_file:
+        class: Knp\UniMail\Cid\Resolver\LocalFile
+        arguments:
+            - %knp_unimail.attachments_directory%
+
+    knp_unimail.cid.resolver.remove_file:
+        class: Knp\UniMail\Cid\Resolver\RemoteFile
+        arguments:
+            - %knp_unimail.attachments_directory%
diff --git a/src/Knp/UniMail/Twig/CidExtension.php b/src/Knp/UniMail/Twig/CidExtension.php
index dc3369c..0afe091 100644
--- a/src/Knp/UniMail/Twig/CidExtension.php
+++ b/src/Knp/UniMail/Twig/CidExtension.php
@@ -3,7 +3,8 @@
 namespace Knp\UniMail\Twig;
 
 use Doctrine\Common\Collections\ArrayCollection;
-use Swift_EmbeddedFile;
+use Knp\UniMail\Cid\Collection;
+use Knp\UniMail\Cid\Resolver;
 use Twig_Extension;
 use Twig_SimpleFunction;
 
@@ -15,18 +16,18 @@ class CidExtension extends Twig_Extension
     private $cids;
 
     /**
-     * @var string
+     * @var Resolver[]
      */
-    private $directory;
+    private $resolvers;
 
     /**
-     * @param ArrayCollection $cids
-     * @param string          $directory
+     * @param Collection $cids
+     * @param Resolver[] $resolvers
      */
-    public function __construct(ArrayCollection $cids, $directory)
+    public function __construct(Collection $cids, array $resolvers)
     {
         $this->cids      = $cids;
-        $this->directory = $directory;
+        $this->resolvers = $resolvers;
     }
 
     /**
@@ -39,19 +40,28 @@ public function getFunctions()
         ];
     }
 
+    /**
+     * @param string $path
+     *
+     * @return string
+     */
     public function addCid($path)
     {
-        $path = str_replace('/', DIRECTORY_SEPARATOR, $path);
-
-        $attachment = Swift_EmbeddedFile::fromPath(sprintf('%s%s%s', $this->directory, DIRECTORY_SEPARATOR, $path));
-        $attachment->setDisposition('inline');
+        foreach ($this->resolvers as $resolver) {
+            if (null !== $attachment = $resolver->createFromString($path)) {
+                $attachment->setDisposition('inline');
+                $this->cids->add($attachment);
 
-        $parts                   = explode(DIRECTORY_SEPARATOR, $path);
-        $this->cids[end($parts)] = $attachment;
+                return sprintf('cid:%s', $attachment->getId());
+            }
+        }
 
-        return sprintf('cid:%s', $attachment->getId());
+        throw new \RuntimeException(sprintf('Can\'t resolve cid from "%s".', $path));
     }
 
+    /**
+     * {@inheritdoc}
+     */
     public function getName()
     {
         return 'knp_unimail.cids';