How to speedup slow Mozilla Thunderbird email client on Windows 7
Worked for me, reposting.
Edit Thunderbird options under Preferences → Advanced → General tab, click on “Advanced options” button and set these values:
layers.acceleration.disabled = true
gfx.direct2d.disabled = false
restart Thunderbird.
Disable AeroGlass: Install the “NoGlass” Addon which is available in the Thunderbird addon repository.
Disable Folder Indexing:
If you have folders with many emails inside, Indexing can slow down Thunderbird. Go To Preferences → Advanced → General tab and disable the Global search.
Cleanup Thunderbird index files:
Thunderbird creates a lot of index files. A cleanup of these files can speedup Thunderbird as well, especially if some of them are broken. There is a handy tool called ThunderFix to do that.
or here thunderfix