Our developers have released the new Spark 2.9.8 update with a fix of garbled text being sent in Spark versions 2.9.0 and newer. Emails with attachments that are sent from Exchange/Office 365 were corrupted and looked like a list of numbers, letters and symbols. 

To install the new version, please open the App Store > search for Spark > open Spark's page instead of Updates tab and install the update. If the update can't be installed, we kindly ask you to consider deleting and reinstalling Spark. This should allow you to access the latest Spark 2.9.8 update.