Check all the account settings to make sure nothing was changed (Specific options to pay closer attention to listed below).
1. Click on the Gear
2. Choose Mail under “Your App Settings”
3. Then look at all of the account settings in the menu on the left.
Specific Account Settings to Review:
Forwarding – Make sure that forwarding was not setup on the account. If it has, please choose the “Stop Forwarding” option and click on the Save button.
Inbox and Sweep Rules – Make sure that there are no rules that have been created. Often if the user states they are not receiving any emails then there has been rule will automatically send all emails to the deleted folder.
Block or Allow – Make sure that there are no unintended entries in the “Blocked Senders” list.