Disabling Outgoing Mail
In WHMCS 8.1 and later, you can easily disable all outgoing mail in your WHMCS installation with one simple setting.
When Should I Use This?
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 WHMCS 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.