Very hitchy and slow with large folders, particularly in search. I find the search usability very poor. Some dumb defaults like the quick filter searching on Se

Very hitchy and slow with large folders, particularly in search. I find the search usability very poor. Some dumb defaults like the quick filter searching on Sender for a folder that's a Sent folder, instead of Recipient. Gigantic memory leaks for me under Linux. (If I leave it open for a few days it'll go > 10 gigs of RAM, that bug's been unresolved for me for over a decade.) Buggy network probing when setting up a new account aimed at an IMAP/SMTP server. Doesn't autofit images to the window size when I'm pasting them into a new email, so with big pictures it's a big hassle to scroll around and manipulate the document. And those are just off the top of my head.