diff --git a/docs/tools/debugging.md b/docs/tools/debugging.md
index dc6e3828d1a4429bdd088f01cc07bd2f5549391f..b68e1cb38f3093182506de5e902f188037583e59 100644
--- a/docs/tools/debugging.md
+++ b/docs/tools/debugging.md
@@ -52,6 +52,8 @@ The following values can be added to your site's settings file `civicrm.settings
 
 - `define('CIVICRM_MAIL_LOG', '/dev/null');` causes all outbound emails to be discarded. No email is sent and emails are not written to disk.
 
+- `define('CIVICRM_MAIL_LOG_AND_SEND', 1);` causes all outbound CiviCRM email to be written to a log file if `CIVICRM_MAIL_LOG` is set. Email will ALSO be sent using the configured method if this is set.
+
 - `define('CIVICRM_DEBUG_LOG_QUERY', 1);` outputs all SQL queries to a log file.
 
 - `define('CIVICRM_DEBUG_LOG_QUERY', 'backtrace');` will include a backtrace of the PHP functions that led to the query.