You can notify your colleagues in Teamleader Focus by using the @ symbol in the 'Activities' in Companies, Contacts, Tasks, Meetings, Projects, Invoices and Products:

When notifying your colleague(s) in a task, you'll also have the possibility to add an attachment.

Furthermore, you can also use the @ symbol in the history of the deal and add a note.

The person that is mentioned in the note will now receive a notification via the bell and an email. 

If you don't want to receive notifications emails, go to your user icon in the top right-hand corner > my profile > notifications to deactivate it. Read more about deactivating notifications in this article