Index: core/kernel/utility/email_send.php
===================================================================
--- core/kernel/utility/email_send.php
+++ core/kernel/utility/email_send.php
@@ -610,6 +610,24 @@
 		}
 
 		/**
+		 * Detects if such part already was added.
+		 *
+		 * @param array $part_definition Part definition.
+		 *
+		 * @return boolean
+		 */
+		protected function HasPart(array $part_definition)
+		{
+			foreach ( $this->parts as $part ) {
+				if ( $part === $part_definition ) {
+					return true;
+				}
+			}
+
+			return false;
+		}
+
+		/**
 		 * Returns text version of HTML document
 		 *
 		 * @param string $html
@@ -780,6 +798,11 @@
 			}
 
 			$definition =& $this->GetFileDefinition($definition);
+
+			if ( $this->HasPart($definition) ) {
+				return false;
+			}
+
 			$part_number = $this->AddPart($definition);
 
 			if ($inline) {