To stay updated when a SharePoint document or an item on your site changes, create an alert .
You can set up an alert for a list, library, folder, file, or list item. For example, you can set up an alert for a specific folder in a library, without having to receive alerts about other items in the library.
Note: Notifications may take up to 4 hours to be received.
Other ways to do notifications:
You can get an alert whenever a file, link, or folder is changed in a SharePoint document library. Depending on the item (file, folder, link), you might see different options when you set an alert.
If you'd rather not get email, but still want to keep on top of changes in your document libraries, see File activity in a document library.
Note: System generated emails from SharePoint workflows and alerts are sent from no-reply@sharepointonline.com address with a display name of "SharePoint Online".
Important: Before you can receive an alert as an e-mail message, a server admin must configure outgoing e-mail in SharePoint Central Administration. Similarly, before you can receive an alert as a text message, a server admin must enable the SMS/MMS service settings in Central Administration.
To set an alert for a document, select the document, select Files or Documents, select Alert Me, and then select Set alert on this document.
To set an alert on a list item, select the item, select the Items tab, select Alert Me, and then select Set alert on this item.
Note: The exact names of the tabs and buttons in steps 1 and 2 vary if you are in a specialized library or list, such as a picture library, tasks list, or calendar list. For example, a calendar list has Events and Calendar tabs where you can find Alert Me.
Depending on how your site and servers are set up, the user you created an alert for might receive an email message that confirms that you created an alert. The alert email might provide links to the list or library, alert settings, the name of the user who created the alert, a mobile view, and other information and commands.
Note: The exact names of the tabs vary if you are in a specialized list, such as a tasks list or calendar list. For example, a calendar list has Events and Calendar tabs where you can find Alert Me.
For info about how to configure outgoing email, or the SMS service, see Configure outgoing email for a SharePoint Server farm.