The "Global Newsletter" feature will let you send massive emails or sms to all or a selected group of users.

This features is available only to platform superadministrators and administrators, and works in three basic steps:
Compose your email
Select the recipients
Send the email

The system will open the user selection page letting you select either:
Multiple single users
Massive select all users from some org-chart nodes
Massive select all users in a group
Massive select all users by company role