Enable Or Disable All Alerts In SQL Server

Enable all alerts

SELECT 'exec msdb..sp_update_alert @name = '''+NAME+''', @enabled = 1' 
FROM MSDB..SYSALERTS

Disable all alerts

SELECT 'exec msdb..sp_update_alert @name = '''+NAME+''', @enabled = 0' 
FROM MSDB..SYSALERTS