Gmail, Outlook.com/O365/etc, are designed for you to "keep everything." Problem is that all desktop email clients aren't designed that way, they want you to have a very small limited subset of email that they can index and constantly have in memory.
When these two worlds converge desktop clients choke and choke hard. Outlook is so terrible that it almost needs to be completely retired. They've barely updated it in ten years.
Best case scenario right now is full webmail (with anyone) and browser notifications for new email etc if you need that.
with large amounts of mail (~90k in one of my inboxes - and if someone asks just yesterday I had to go and fetch some info from a 2007 mail), GMail chokes much more than thunderbird, e.g. it takes 2/3 minutes and sometimes does not work to mark a large set of email as read/archived/whatever while this is almost instant with TB.
the default answer to op's question in enterprise land (where windows is still treading for relevancy) is Outlook.
thunderbird suffers the issues the comment mentions above -- barfs with large dbs, no support for exchange, not sure if it even supports push notifications, etc
it should be noted that mail on mac works well and the win 10 mail app this article is all about works pretty well too, which is why its a travesty MS is going to ruin it.
I have over 20 years of email stored locally in Postbox. I've kept every non-spam email since I first got online in 1997. I regularly use it to search for things people sent me (or I sent them) months or even years ago. It's really not a problem at all.
I've got Postbox open right now and it's using 625MB RAM. (That's a lot compared to the Eudora days, but I have 16GB RAM now.)
A desktop client on your laptop also means you can write emails & be able to search your email history while in flight mode, and queue the messages to be sent when you land & have WiFi again.
I use Mailmate. It’s everything I wanted Thunderbird to be.
I swear half of the clients on the market turn out to support only a small list of authentication methods, or don't let you specify port!
It is of course overkill though if you have one email account and only process a couple emails a day.
i still dont think it supports the iCalendar/calDAV standard either.
It's too easy to write a backhanded comment regarding this issue, but it's just really annoying.
If you do feel that's a lot, try the demo first to see if you like it, and maybe wait for Black Friday in case they have a sale.
I'd like an alternative that has close to tray functionality.
15 years later and 3 major windows iterations later and we still don't have it.