How to set Alert in Document Library or Custom List
Step 1: Go to the any document library or list where you want to set the
alert.
Step 2: Then click library or list on top of the ribbon.
Step 3: To set an alert for a document or list item, select the document
or item and then click Files > Alert Me > Set alert on this document or click
Items > Alert Me > Set alert on this item, depending on whether you are working
with a library or a list.
Step 4: Set Users who want show the mail and change everything according
to your requirement then OK.