diff --git a/apps/voicemail/etc/voicemail.conf b/apps/voicemail/etc/voicemail.conf
index 5724b84e..9aede97e 100644
--- a/apps/voicemail/etc/voicemail.conf
+++ b/apps/voicemail/etc/voicemail.conf
@@ -13,3 +13,11 @@ max_record_time=30
 #CFGOPTION_SEMS_TEMPLATEDIR
 email_template_path=/usr/local/etc/sems/
 #ENDCFGOPTION
+
+# rec_file_ext : extension to recorded file, determines file
+# format (wav, mp3; need mp3 plugin loaded for mp3)
+# default is 'wav'
+#
+# example: 
+#   rec_file_ext=mp3
+#