Navigate to: Dev Center -> Global Settings -> Inventory Subscription Notification Settings 

Administrators have the flexibility to define the days when should the email records be deleted from the Database for the emails which are already been sent to the Customers.

Inventory Subscription Notification Settings have the following two options:

1. Delete Already Sent Emails - This setting allows Administrators to decide when should the already sent email records should be deleted, by default 5 days are considered.
2. Delete Pending Emails With Awaiting Inventory - This setting allows Administrators to decide when should the pending email records where inventory is still awaiting to be restocked should be deleted.
   For example: if a user has subscribed for an Out of stock product and the product is not restocked for a longer period of time then the particular record should be deleted. (By default, 90 days are to be considered).