Every user can define their own email preferences of which there are 2 areas, General Settings & Workspace Settings.
If users have selected "never" within the (Workspace Settings) area, that will not affect private messages as they would still receive them.
* This area only affects the main changes which are new documents, blog articles, web pages links, discussion forum messages, and surveys.
Whereas, it's the checkbox option within the (General Settings) area that would stop the private messages being sent to them, see below.
* If users were to untick the top checkbox above, that would then stop users from receiving any private messages on the platform.
Kahootz Tip: For more information on What Alerts & Notifications are sent via eMail Preferences - click here.
However as a manager, if you need to send a message out to all users regardless of their preferences then you can use the "send email as manager" option.
Go into the workspace and select "Send Email as Manager" from the (Manage Workspace) drop-down, shown above and then remember to tick Broadcast.
As shown above, this will then send an email to everyone in that Workspace regardless of their email preferences.