You’d think that there would be solid alternatives, but you’d be wrong. And you’d be wrong because email clients are no longer focused on the power user.
That shouldn’t be surprising. Purchase any new computer or iOS or Android device and you get a free email client that satisfies the needs of the vast majority of users who demand little more than to send and retrieve messages through common email services. What sort of market does that leave for someone wishing to build a truly powerful email client (something, I understand, that is both difficult and time consuming)?
These days I find Apple Mail—combined with plug-ins, AppleScripts, and EagleFiler—to be the least bad option. However, I’ve been following the development of MailMate with interest. At least one other developer has a power-user e-mail client in the works.