The 'fix' is to have fewer messages to index. It's a tradeoff issue. With indexing turned off, you can still search.

The 'fix' is to have fewer messages to index. It's a tradeoff issue. With indexing turned off, you can still search.

200 GB sounds like a lot, but more important is the number of messages - because Gloda only indexes (reads) the first 40k of a message). 300K messages is a lot, but shouldn't take more than a day. But it also shouldn't make your system miserable.

So I think here indexing is a symptom, which is to say there is an underlying cause which must be resolved.

One possible cause is antivirus, but there are more, including possible bug in Thunderbird. To start off,

• Start Windows in safe mode with networking enabled https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode
• Still in Windows safe mode, start Thunderbird in Troubleshoot mode https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird

Does the problem change?

Thank you for the suggestions. Here's what I've found:

Disabling indexing makes the global search (CTRL+K) unavailable, meaning Thunderbird doesn't offer any search functionality without it. Therefore, indexing is essential.

Disabling my antivirus (ESET) didn’t help. I decided to give Thunderbird a chance to index all messages. This time, I noticed that after closing the program, indexing resumes rather than starting over. This might be because I disabled email program monitoring in ESET.

Thunderbird indexed about 5,000 messages per hour, and after around 2.5 days, it managed to complete the process. Currently, the program works faster (like when indexing was off), but there are moments, especially when downloading new messages or "bringing a folder up to date", where it slows down significantly and lags and freezing for 1-2 seconds. While it’s annoying, it’s not as slow as it was during the indexing process.

For reference, the folder at `C:\Users\(...)\AppData\Roaming\thunderbird\` now takes up 165 GB. Power mode (silent, entertainment, performance) does not make a difference, meaning increased power does not speed up Thunderbird.

I haven’t tested safe mode yet. Do you think it’s worth trying safe mode with networking, and/or should I take other steps?

First, I defer to Wayne, as I am not a performance specialist -- but I have opinions that may or may not prove useful. One option might be to set properties of folders that are not needed for indexing to be exempt from indexing. Another possibility might be to have global index file on a different drive from the message folder.