Good Desktop Companion to Outlook for iOS

So I really like Outlook (Acompli) for iOS, and I want to be able to have similar functionality on my Mac. Does anyone have suggestions? I'm flexible with e-mail providers. Should I just switch to Mailbox? I've been hesitant to do so because Mailbox is so slow with putting out updates and bug fixes (unlike Dropbox, which is insanely stable and very fast to put out updates). I mean, the Mailbox app hasn't left beta and it's been so many months (or years even!)