Update documentation

Documentation/AdministratorManual/Index.rst

@@ -77,6 +77,23 @@ Configure Email Handling
    Default
          ``[email protected]``
 
+.. container:: table-row
+
+   Property
+         email.keepLocalFilesForDebugging
+
+   Data type
+         string
+
+   Description
+         Keep files (.ics, .csv, .html) sent by email for debugging purpose.
+         The files are stored in :code:`typo3temp/tx_slubevents/`.
+
+         **Do not use this setting on production environment!**
+
+   Default
+         0 - Do not keep files.
+
 .. container:: table-row
 
    Property
@@ -273,4 +290,4 @@ simply add these line to your registration form template
       </label>
 
 While the property ``acceptpp`` is submitted, it's needed to be checked
-to submit a valid registration.
+to submit a valid registration.