Using the @all command will notify all users within the owner company when creating a new conversation. If used in an already created conversation/channel, all users within that conversation/room will be notified
Note: This also includes users who are offline.
Using the @online command will notify users who are active at the time of sending your message, be it a new conversation or within an existing conversation/room.
Using the @username will notify only that user.
Within Teamwork Chat, when it comes to sending a message, there are various ways to notify individuals or groups based on whether they’re online or away:
Note: If you're unable to @mention a user within a conversation/channel, this is usually a result of a firewall issue.
Users can receive notification in 3 ways;
Desktop notifications: will be sent to the desktop when you are logged into Teamwork Chat, currently active on the site & when a user "@"mentions or @all is used
Email notifications: will be sent via email when you are away from your machine and not active.
Push notifications: are available through the iOS and Android Apps, when you initially login to the app you will be given the option to receive these or not.
For more information on notifications see Notification settings