diff --git a/htdocs/core/class/conf.class.php b/htdocs/core/class/conf.class.php
index 1692b58c5f9..08763cc346b 100644
--- a/htdocs/core/class/conf.class.php
+++ b/htdocs/core/class/conf.class.php
@@ -390,7 +390,8 @@ class Conf
 		// Set some default values
 
 		$this->global->MAIN_ACTIVATE_HTML5=1;
-
+        $this->global->MAIN_MAIL_USE_MULTI_PART=1;
+        
 		// societe
 		if (empty($this->global->SOCIETE_CODECLIENT_ADDON))       $this->global->SOCIETE_CODECLIENT_ADDON="mod_codeclient_leopard";
 		if (empty($this->global->SOCIETE_CODECOMPTA_ADDON))       $this->global->SOCIETE_CODECOMPTA_ADDON="mod_codecompta_panicum";