alt Hacker NewsmacOS mail app is a special type of terrible especially if you deal with multiple email accounts. Every os upgrade causes various bugs such as search index all of the sudden not working and you have to reset and reimport all your mailboxes
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I've used Mail.app since 2004 and have not had any of those problems except searching using Spotlight have occasionally been broken over the years, but never searching within the app.
And I've had both multiple accounts various servers both private and work. And dozens of work-related role aliases which Mail.app correctly always used when replying. No problems there. Neither I have had to rebuild sqlite mail folder db, but did have some quirks first when work emails were transferred to Office365 which wanted to rename folders etc. nuisance, 2FA worked also worked fine since IIRC Mojave. I've had some addons MacGPG, sorting and maintenance scripts too. MacGPG does need some attention when upgrading though besides paying for subscription it moved time ago.
I've used also Thunderbird, mostly with linux. And used and tested whole lot of various clients since Elm was a thing -80's, then Pine, mutt etc.
The macOS Mail.app is fast reliable in my opinion, but sure there are things in its UX it could be yet improved. But still it's been long time among best and never broken or let me down over 20 years, both work and private use.
I agree. Mail.app is one of the buggiest pieces of software I have ever used. It has some nice features as well, especially the editor. But some of the bugs I have experienced were catastrophic, such as silently failing exports that appeared to have completed successfully (this was recently fixed after years).