Fix link typo. Closes #17

Author: axilleas

install/centos/README.md

@@ -170,7 +170,7 @@ mail server. The recommended one is postfix and you can install it with:
 
     yum -y install postfix
 
-To use and configure sendmail instead of postfix see [Advanced Email Configurations](configure_email.md).
+To use and configure sendmail instead of postfix see [Advanced Email Configurations](e-mail/configure_email.md).
 
 ### Configure the default editor