diff --git a/application/config/mail.php b/application/config/mail.php
index e7fd53c3a..4f1baa85d 100644
--- a/application/config/mail.php
+++ b/application/config/mail.php
@@ -34,16 +34,16 @@ $config['validate'] = false; // If true then the email address will be validated
 $config['enable_debug'] = false;
 
 // default sender
-$config['sancho_mail_default_sender'] = SANCHO_MAIL_DEFAULT_SENDER;
+$config['sancho_mail_default_sender'] = defined('SANCHO_MAIL_DEFAULT_SENDER') ? SANCHO_MAIL_DEFAULT_SENDER : '';
 
 // If to use images for custom mails
-$config['sancho_mail_use_images'] = SANCHO_MAIL_USE_IMAGES;
+$config['sancho_mail_use_images'] = defined('SANCHO_MAIL_USE_IMAGES') ? SANCHO_MAIL_USE_IMAGES : false;
 
 // image path for sancho mail, relativ to document root
-$config['sancho_mail_img_path'] = SANCHO_MAIL_IMG_PATH;
+$config['sancho_mail_img_path'] = defined('SANCHO_MAIL_IMG_PATH') ? SANCHO_MAIL_IMG_PATH : '';
 
 // header image for custom mails
-$config['sancho_mail_header_img'] = SANCHO_MAIL_HEADER_IMG;
+$config['sancho_mail_header_img'] = defined('SANCHO_MAIL_HEADER_IMG') ? SANCHO_MAIL_HEADER_IMG : '';
 
 // footer image for custom mails
-$config['sancho_mail_footer_img'] = SANCHO_MAIL_FOOTER_IMG;
+$config['sancho_mail_footer_img'] = defined('SANCHO_MAIL_FOOTER_IMG') ? SANCHO_MAIL_FOOTER_IMG : '';