diff --git a/lib/Horde/ActiveSync/Imap/Message.php b/lib/Horde/ActiveSync/Imap/Message.php
index be123683..0e16a7dd 100644
--- a/lib/Horde/ActiveSync/Imap/Message.php
+++ b/lib/Horde/ActiveSync/Imap/Message.php
@@ -741,7 +741,15 @@ public function getSubject()
      */
     public function getDate()
     {
-        return new Horde_Date((string)$this->envelope->date);
+        $date = $this->envelope->date;
+
+        // Newer IMAP envelope handling may provide a Unix timestamp as string.
+        // Horde_Date accepts int timestamps but not numeric timestamp strings.
+        if (is_string($date) && ctype_digit($date)) {
+            return new Horde_Date((int)$date);
+        }
+
+        return new Horde_Date((string)$date);
     }
 
     /**