Hi Meysam,
Thank you for posting in our forums.
Yes you can style the inbox components using AppStylist. You can find the inbox controls from the “InboxControls” tab in AppStylist and you can modify their appearance from there. After that add an InboxControlStyler component to your forms and the changes that you have made in the ISL files will be applied to the inbox controls once you load it. Note that the styling options for the inbox controls are more limited simply because the controls themselves don’t offer the extensive styling options the Infragistics controls do.
I have attached a small sample which demonstrates this suggestion.
Please let me know if you have any additional questions.