Client like thunderbird is good if you always use the same desktop/laptop machine to do your email. If you are using multiple devices like school, friend, work, library or even mobile it totally breaks down. To say nothing of system failures, breaking or losing the machine etc.
Most people who love TB have a setup that has been stable for 20 years. Good for them, it suits their needs. But the contempt with which they seem to hold the majority of the population for whom TB would be a totally unsuitable choice is rather unpleasent.
Ever notice how rarely you see someone saying "I switched to TB from webmail 2 years ago and its great"?
Too bad, as i would absolutely love to switch the floss desktop/mobile clients and have tried to do so on a few occasions. They are simply not compatible with modern communications habits.
I'm a heavy Thunderbird user and to be honest, I don't understand what you're saying at all? I have multiple private mail accounts and a work mail account and I use all of them on multiple machines with Thunderbird but also with different clients (e.g. FairEmail on Android) as well as webmail (at least for my work mail I use it sometimes) and I never experienced any problems. What exactly do you mean? I mean, I do have an export of my thunderbird profiles (maybe not up to date, though, tbh), but more so out of comfort than necessity. Without this export, and in the unlikely case of a system failure, I would have to go through the process of adding my mail accounts (server, password, username) by hand and that's basically it
Sorry, I kind of forgot about lemmy or a few days. In Thunderbird, I create a new dedicated folder, use Tools --> Message Filters. I then can add the desired filter (something like must contain at least 'host.tld' in sender) and make it move all filtered mails into the previously created folder. I just checked, it works like this. You can also specify when that filter should be executed (e.g. when getting new mails or every 10 minutes) and the folder with the filtered mails also shows up in FairMail on Android.
Better description: https://support.mozilla.org/en-US/kb/organize-your-messages-using-filters
As someone else pointed out, maybe you're thinking of POP instead of IMAP? I basically have all my mails on the host's servers (including folders) and just synchronize using my different clients
I use Thunderbird on several machines, and I use broadly the default config (no fancy business). I also have the same email accounts set up on my Android phone (Gmail ones on the native Gmail client app, an Outlook one on the Outlook app). When accessing my email on a machine which doesn't have Thunderbird set up for me (such as my corporate laptop), I just use the webmail interfaces.
And it all works...fine. why wouldn't it? Thunderbird and the Android apps just send their service calls off via IMAP and it all sorts itself out without any fuss from me. All the data lives off in the cloud anyway; it's just a different way to interact with it other than the web interface.
I just happen to like having all my email accounts in one combined place, running in the background and throwing system notifications.
I think they're expecting thunderbird users to use POP instead of imap, Gmail integration, OWA, or other protocol that expects the mail to stay on the server.
Leaving the mail on the server has been great in Thunderbird since the Mozilla days. I did jump to Gmail web app a long time ago though. I'm assuming Gmail support has improved in the last 15 years?