What aspects of the UX do you think that needs improvement? For me the default layout (sidebar for email accounts and folders, upper frame for email list and lower frame for single email) looks very good. The pain is in finding the setting that I need to adjust and specifying criteria for searching emails. However if the improvement is only about making it look better, then I wouldn't buy it because "modern" designs consume more screen space and GPU. Better to have Hacker News than Discourse.