Yup. I still don't see why everyone complains about current mail clients. Mail.app on OS X / iOS, Outlook on Windows, works for me.
To make me switch, you would have to show me why the new thing was so much better. Like how Google search results were always better than Yahoo! (IMHO, no objective measurements used) so I switched. You would also have to explain it in a sentence I could immediately understand, whereas all the recent clients I've ready about either (a) claim to make things better but don't tell/show me how before I get bored of the page, or (b) use manager speak that I can't understand or is vague and abstract promises to increase collaboration or something. Therefore I've given almost no attention to any recent attempt to change email.
There's a big distance between "works for me" and "delights me."
I use Thunderbird on Linux and Windows. It "works for me," in the sense that it's stable and predictable and doesn't lose my data. But it also has lots of niggly little problems that annoy me, like UI decisions that made more sense ten years ago than they do today and limited tools to support people like me who have a ton of mail.
So while I use and recommend Thunderbird, I also would love to see something come along that is so much better that it makes me fall in love with it, instead of just shrugging my shoulders and resigning myself to this being as good as things get.
How much are you looking to pay for this? How many people are looking for delight in their email client? Do these numbers multiplied add up to a few tens of millions?
To make me switch, you would have to show me why the new thing was so much better. Like how Google search results were always better than Yahoo! (IMHO, no objective measurements used) so I switched. You would also have to explain it in a sentence I could immediately understand, whereas all the recent clients I've ready about either (a) claim to make things better but don't tell/show me how before I get bored of the page, or (b) use manager speak that I can't understand or is vague and abstract promises to increase collaboration or something. Therefore I've given almost no attention to any recent attempt to change email.