In SharePoint one can subscribe to any document libraray or list to be sent alerts when changes occur such us additions, deletions, and updates. This is done by choosing "Actions" => "Alert Me".
If one wishes not to receive alerts anymore, it is not that apparent how to do it. Well, you would need to go to "Site Actions" => "Site Settings" => "User Alerts". Choose the user in question and subsequently delete him/her from the appropriate list or document library alert.