Update index.md

added FAQ regarding email notifications feature

Author: muhammadatifjav

src/connections/reverse-etl/index.md

@@ -303,3 +303,11 @@ Column JSON size | The maximum size of any single column value. | 128 KiB
 
 #### Why do my sync results show *No records extracted* when I select *Updated records* after I enable the mapping? 
 It's expected that when you select **Updated records** the records do not change after the first sync. During the first sync, the reverse ETL system calculates a snapshot of all the results and creates records in the `_segment_reverse_etl` schema. All the records are considered as *Added records* instead of *Updated records* at this time. The records can only meet the *Updated records* condition when the underlying values change after the first sync completes.
+
+#### Can I be notified when Reverse ETL syncs fail?
+Yes, you can sign up for Reverse ETL sync notifications:
+
+1. Open the Segment app.
+2. Go to Settings > User Preferences.
+3. In the Activity Notifications section, select 'Reverse ETL'.
+4. Enable 'Reverse ETL Sync Failed'.