Outlook

• hides email address => security issue; eases phishing (even beyond not showing whether it's ensured valid)
• can't have an inbox filter that moves emails and gives you a normal notification of unread email
• can't have an inbox filter that is both server side and gives a desktop notification
• can't save your reply email next to the replied to email in the inbox - but can in the folders
• can't handle specific column orders (was it category before date then not working? sth like that)

I switched / had to switch at work. It works. I got used to it for the most part. But I'd much prefer using Thunderbird.

Because I'm using both now in both I never intuitively navigate to the delete button. Because the layout is different between the two.