Processing client requests for duplicate-free server operations is particularly useful for creating and sending items using Microsoft Exchange Web Services (EWS). The system facilitates avoiding creation and sending of duplicate items. In contrast to conventional implementations that send a single command to create and then perform subsequent processing of an item, a feature of the present embodiment is using two commands: a first command to create the item, and a second command to subsequently process the item. In a specific implementation, an EWS item's provided ChangeKey property is used to keep track of the EWS's reply from the server to the client, thereby avoiding duplicate item creation.