When to Use?
If you want to tell people about changes you made to a meeting on Outlook, you can use the @mentions feature. This will send them a message straight to their inbox.
Procedure
When you change your meeting, attendees will get a notification and can look at the details to see the changes, but they won't get an email in their inbox. If you want them to get an email, you need to use @mentions. All you have to do is write their name after the @ symbol (like @attendee1 or @attendee2) in the meeting's message.
For more information see: Use @mentions to get someone's attention - Microsoft Support