In WHASOLS, you can easily disable all outgoing mail in your WHASOLS installation with one simple setting. 

Sometimes, you may need to ensure that client and system communications are paused. This feature allows you to quietly test customization, verify new system changes, or perform other operational routines without needing to change to your mail system settings or external setup.

Because this will prevent WHASOLS from sending any email, make sure to toggle the setting to OFF as soon as you're done with these activities. Otherwise, customers won't receive important emails from you, like payment reminders and purchase confirmations.

To disable outgoing mail on your WHASOLS installation, go to Configuration > General Settings, click the Mail tab, and set the Disable Email Sending toggle to ON.

While this setting is enabled, the system will log an error at Logs > System Logs each time that you enable or disable this setting.