Typically, when you manage multiple markets and vendors the amount of email notifications will increase with the growth of your markets. Each vendor within a market will generate a set of notifications based on when you assign stalls, send out invoices, communicate through application comments and other system level events. If you are part of an organization you may only care about the market that pertains to you and making those adjustments is easy.
In your Farmspread account, click on your user at the top right of the page (#1), next click on Notifications (#2) in the left hand navigation, finally clicking on the markets and vendors (#3) you wish to receive email notfications for. The green checkmark in the toggle means you want to receive those emails for that market or vendor and the red xmark means you don't want to receive those notifications.