The clean install clears all your preferences and removes all accounts added to Spark.
Follow these steps to perform a clean install:
Open Finder and hold the alt button.
On the top menu bar, select Go > Library.
Open the Group Containers folder.
Find and select the folder 3L68KQB4HG.group.com.readdle.smartemail. If you use the beta version of Spark, select the folder 3L68KQB4HG.group.com.readdle.beta.Spark-Mac.
Right-click on the folder and select Move to Trash.