MailMate is by far my fav. A true traditional IMAP mail client with killer search, PGP support native, keyboard short cuts, great multi-account support, etc etc. Its not an easy to use mail client, its very much a power users tool and takes some time to adjust too. But after you get used to it its hard to use anything else.
Mailmate is what I use. It isn't free, but it runs completely locally, no cloud anything. It's also got extremely powerful search/smart mailbox functionality. If you liked Thunderbird, you'll probably find MailMate to be similar, they're both "old-fashioned" mail clients in a way.
The biggest limitations of MailMate is that it only supports IMAP, no Exchange or POP. It's got some special support for Gmail's unique implementation, but otherwise it's IMAP or nothing. When sending email, it uses Markdown, so you'll need to be familiar with that to send more than plain-text (and if you do a lot of rich HTML/image sending, it might be cumbersome.)
There aren't a lot of other non-cloud email clients that I know of. Mail.app is the only other one that comes to mind. The latest trend is toward cloud-based, and those require a server somewhere to have access to your stuff.
I'd recommend you take a look at Postbox. It's what I'm currently using and quite happy with it. On the other hand, if you want sheer power and flexibility, you can't really beat Mailmate
Unfortunately, there aren't that many great options I can recommend on iOS, so I just stick with stock mail app (or fastmail + gmail apps) and use one of the apps I mentioned on MacOS
MailMate isn't the prettiest, but I have found it to be the most powerful and customizable for power users. It's email filtering has no competition. The developer is responsive and seems to fully understand the email spec inside and out.
That's a blast from the past. I remember looking at MailMate https://freron.com many years ago. I think at the time it didn't do HTML at all. I'm going to get a demo and expect it to look at home in System 9.
Using MailMate to replace Apple Mail. I would use the Apple Mail app but it frequently spontaneously opens for no reason. This glitch has been happening for years with no fix from Apple and I have tried several other suggested fixes, nothing works. This pretty much makes the Apple mail app unusable for me, so I find MailMate is the best alternative.
>> Does anyone know of any good desktop email apps with smart mailboxes (i.e. folders with filters)?
> The smart mailboxes and filtering features of MailMate are probably the most powerful that I have ever found in a graphical mail app.
I second that. MailMate is by far the best e-mail client for MacOS, in my opinion. Fully focused on IMAP, with a very responsive developer.
One of the few things it is missing, is an easy way to store e-mails locally.
The mail client I've used for years is MailMate. It's extremely flexible in that you can define your own keyboard shortcuts and it supports tagging in a useful way.
This app is hands down the best mail app that I’ve ever used. It may not be the prettiest thing, but it is power and extremely fast. I cannot recommend it enough. My favorite features are the rules/mailbox engine which is really powerful as well as the ability to edit mail in Markdown.
3GB? Wow. Yeah a native application should use a lot less RAM. I have a business and personal e-mail account associated with my native client of choice(MailMate), and it takes 300MB of RAM.
I'm sure I tried Airmail. Can't remember why I ditched it, tbh. Will look into EasilyDo Mail.
On OS X, it's MailMate all the way. Airmail is a puny toy by comparison. Like, literally a toy. (Unless you use Gmail, I guess.)
MailMate is by far the best email client I have ever used (also is PGP friendly). But it does cost $50. And a great email ad on is SpamSieve which filters out spam email for you. This utility cost $30. I find them both incredibly useful. Especially because I use email daily.
https://freron.com/ MailMate http://c-command.com/spamsieve/ SpamSieve