At (@) Mentions in Notes fields
Using the settings above from Record-level Editable Notes field, internal users with Full licenses may communicate with other internal users (no external parties) from Notes fields utilizing At (@) Mentions. Users mentioned will receive an email notification and an alert through the Unread Mentions icon 
on their Homepage, as seen in the graphic below:
The following are steps to use an @ mention:
Visit the Notes field of any Master grid or sub-grid in a record.
Click into the Notes field and enter text for the note, and then use the @ symbol and a list of other users will appear (as seen below).
Select the user you want to At Mention. Additional users can be selected by typing the @ symbol repeatedly.
Click out of the Notes field after finished entering text.