Comment by nh2

I have ~100k mails in Thunderbird. The GUI always feels a bit sluggish:

Sometimes spinners don't spin, reactions to clicks take ~500 ms, when I switch from Inbox to Calendar for the first time, I can see how the buttons in the top row render one after the other in ~100ms. (I don't think a human should _ever_ see buttons render!)

Sliding around the size of panels renders at 10 FPS, not so cool.

Opening "Account settings" first produces a full white-flash, then a grey-flash (dark mode), and then renders the UI element.

Startup takes ~5 seconds till the GUI fully shows. Then it hangs at "Opening folder INBOX..." for 60 seconds. Not sure why that sync takes so long when there are no new emails.

So it works acceptably but doesn't feel great.

Searching for e.g. "horse" in the Ctrl+K global search and hitting ender takes 5 seconds for full-text search to produce results. I think that part is OK. I mostly use the "Quick Filter" == "Filter messages" == Shift+Ctrl+K instead to search only subjects and correspondents.

I have ~100 IMAP folders (from +suffix emails). Unfortunately Thunderbird doesn't notice when a new folder gets spawned by a new +suffix email, I have to restart it Thunderbird to ever get to see that email.

RAM usage is 900 MB RES on Linux. (I could not check if that's glibc's fault as so often, because Thunderbird crashes when jemalloc is preloaded.)

When I move the mouse cursor around anywhere in the GUI, that causes 90% CPU usage. For comparison, in Sublime Text, moving the mouse cursor around causes 10% CPU usage over the text buffer and 25% over tabs.