There are two places you can manage notifications. The first is managing the notifications for each item.
To manage your Item Notifications:
Go to into any single item by clicking your Watch List, your Bids Page or by just clicking on any item.
Then scroll down on the item page and on the left side of the screen, you'll see the notifications at the bottom. You can toggle them on and off. Remember if you turn off your notifications you will not receive updates when you are outbid!
To manage your Global Notifications:
Go to My Account, then Notifications.
From there you can turn on or off all notifications:
To manage your notifications, go to My Account then Bids, from there you’ll see every item has a switch for SMS and Email. You can turn those notifications off an on there. To manage notifications for an entire auction, navigate to My Account then Notifications.