I use Thunderbird and it has Tag system "Important, Work, Read Later so on" 5 tags and you can make new ones also afaik. I only use the ones that come with it. Its working great

edit: ohh i failed to read "webmail" in there, ignore me then

Check out RoundCube if you haven't already.

Quoting: tuubiCheck out RoundCube if you haven't already.

I actually use that for GOL's main email when I'm not at my desk, works well.

I know of roundcube and as far as email readers go it's not bad - but what Inbox does help your sort through and organize mail quickly;

- it automatically categorizes mail it recognizes ( invoices, receipts, news letters, update mails, spam, etc )
- it has a delete button for getting rid of mails, and an archive button for mails that not relevant anymore but may one day be
- it lets you post pone mails ( or groups of mails ) so you can schedule when to handle it ( you can even put an event or reminder in calendar directly from the mail )
- mails that include .ics files can be added directly to your google calendar ( nice for automatically adding appointments from online booking dentist, car repair, hair dresser, etc )

what it all adds up to is that only the mails that need your attention here and now will be visible and once you've dealt with those it will be nice an empty/distraction free until such time as you scheduled dealing with the various other mails.

It may sound like a small thing, but honestly it has been an absolute beast in combating everyday stress and having it yanked away because google needs to display more adds is really effing anoying :(

Nextcloud Mail, Roundcube, Horde, Open-Xchange are the best self-hosted webmail clients I can think of right away. As far as I know none of these implement any automatic filtering, though.

For filtering what I prefer personally is Sieve and different folders to automatically put the emails in. This depends on Sieve being installed on the server though, and managesieve if you want to manage it from the client.

That might not be an option at all if you're not running your own mail server, but I suppose you could always check with your provider.

Found this - bascially a desktop app that replace inbox by talking to gmail, not ideal but not bad either
https://github.com/denysdovhan/inboxer