The author also maintains a blog where he post quirks about several IMAP implementations. For example, Yahoo IMAP or Gmail labels. The app itself also handled all these edge cases very well.
It is a very fast mail client with near empty mailboxes.
I have a few small gripes with Mail.app (it occasionally claims that some messages are unread that aren't, for instance), but nothing I've seen of other mail clients has led me to think they'd ever be better for my workflow.
I believe there are some plugins that support similar features, but I have not yet found a Mail.app snoozing that is portable as well (eg: Android/webapp support).
It can also be pretty laggy (e.g. selecting multiple messages), but this has gotten a lot better in High Sierra.
I still use it though since I have yet to find an alternative that I prefer (I've only tried a few though)
The obvious tradeoff the relative lack of polish and overhead during initial setup, but if you're willing to put up with that it's a fine choice.
I use it with my personal email (hosted at Hover), and my work email, hosted on some IMAP server.
Works like a charm.
Also has the best "less important emails" inbox implementation that I've used so far. The whole gimmick of an AI bot I could chat with is just that, a gimmick, but bot the desktop and mobile apps are solid.
Wishlist items remaining: Newton had you have a Newton account that would automatically set up all your accounts when you installed it on a new device, but Astro doesn't do that. Also, I'd love it to automatically pick the right account to send from once I type in the recipient's address, based on past correspondence, like Newton did. But neither of these are even small issues.
Overall quite happy with them.
In a more serious note, are you actually using eudora? If so I'd love to hear if there is a still-maintained version as well as the reasons sticking to it.
Eudora was recently donated to the Computer History Museum¹, so there's some faint hope of a revival, although it would more likely be the inferior Windows version.
Sure, they've - allegedly - made it run faster but they've also removed extension support, blocked any ways to hack in a calendar (which could previously be done by adding a permanent browser tab pointing to Google Calendar) and seriously hurt legibility with its new design by removing dividing lines, decreasing contrast across the board and giving all the icons a bright random colour.
A real shame as there are no real alternatives.
Last example of today: Filtering emails whether they have an attachment. A mail with attachments i was searching for was not included in the selection.