Input focus stealing
What the hell is it with the Office 365 web version of Outlook where some random part of its UI suddenly gets focus while you're typing an email and not only swallows several keystrokes but acts on them as commands?! If you're lucky, they just get redirected to the browser UI and you find yourself doing a "search within this page" but sometimes you end up deleting the message you're replying to, archiving another one, snoozing one, emptying the folder...
At first I thought it was either me palming the touchpad on my laptop (although I've never had a problem with that in the past, but maybe the anti-palm thingy had stopped working...) or using an "unsupported configuration" (the laptop runs Linux). Then I had exactly the same problem while using it on a Windows 10 desktop so it can't be either of those things.
I'm seriously tempted to defy the company standard practices and use a real email client.
Biting the hand that feeds IT
