diff -Naur a/smtp.mail.inc b/smtp.mail.inc
--- a/smtp.mail.inc	2013-03-16 23:18:39.000000000 +0100
+++ b/smtp.mail.inc	2013-04-29 12:22:37.333324000 +0200
@@ -441,12 +441,14 @@
     // Process mimemail attachments
     if (isset($message['params']['attachments'])) {
       foreach ($message['params']['attachments'] as $attachment) {
-        if (isset($attachment['filecontent'])) {
-          $mailer->AddStringAttachment($attachment['filecontent'], $attachment['filename'], 'base64', $attachment['filemime']);
-        }
-        if (isset($attachment['filepath'])) {
-          $mailer->AddAttachment($attachment['filepath'], $attachment['filename'], 'base64', $attachment['filemime']);
-        }
+        if (!is_object($attachment)) {
+          if (isset($attachment['filecontent'])) {
+            $mailer->AddStringAttachment($attachment['filecontent'], $attachment['filename'], 'base64', $attachment['filemime']);
+          }
+          if (isset($attachment['filepath'])) {
+            $mailer->AddAttachment($attachment['filepath'], $attachment['filename'], 'base64', $attachment['filemime']);
+          }
+        } 
       }
     }