Yes, when NXPowerLite optimizes file attachments in Exchange items, it changes some properties of the items in question.
To make changes to Exchange, NXPowerLite uses the Microsoft EWS API. All property changes made during the course of optimization result from our using this API; NXPowerLite does not directly alter Exchange data.
Tagging of Exchange items by NXPowerLite
NXPowerLite adds its own item tag to the properties of each item that has at least one attachment successfully optimized. This allows NXPowerLite to potentially skip that item on future optimization runs, resulting in improved performance.
Other properties changed as the result of optimization
During the course of development, we have identified other Exchange item properties that are modified as a result of running NXPowerLite. This list may not be exhaustive, but includes: