Re: Why would anyone tolerate this?
I use Outlook on Windows, Mac, and iOS for business email, 'cause we have Exchange Server around here and every ever so often Something Happens(tm) which causes other clients to hiccup. I use Thunderbird on Windows and Apple Mail on Mac and iOS for personal email. There is no Thunderbird on iOS, and Thunderbird on Mac is even more neglected than Thunderbird on Windows. I'll be replacing Thunderbird soon enough, preferably with a cross-platform Mac/Windows client. I have been testing Edison on iOS; there are a few issues, some of which are allegedly being addressed. We'll see.
I do not use Microsoft Mail, or whatever they call it. I do not use Google Gmail client. I do not use Yahoo mail. Apple doesn't care what users do with Apple Mail. Microsoft, Google, and Yahoo do care. Deeply. Microsoft doesn't appear to be slurping Exchange Server. Yet. I think. In theory Apple Mail can access Exchange Server accounts; Thunderbird can't, unless IMAP is turned on, as Thunderbird doesn't speak Microsoft Weird Mail Thingie(tm). In practice, Microsoft tweaks Exchange Server regularly and just by accident the tweaks might, just might, break Apple Mail. Not every time. Just often enough to be Very Annoying(tm). If Microsoft would stop doing that, I'd use Apple Mail instead of Outlook on Macs and iOS. The two facts may be connected, which is why I only think that Microsoft isn't slurping Exchange Server.