Comment # 4 on bug 1037806 from Fabian Vogt

(In reply to Vadim Krevs from comment #3)
> I've rebuilt kmozillahelper, set the env variable, started TB and clicked on
> several emails that trigger high CPU usage from kmozillahelper. Log is
> attached.
> 
> Please let me know if there is anything else you'd like me to try.

Thanks!

I see a ton of senseless queries for HANDLEREXISTS, so it's a bug in
thunderbird. It could be worked around in kmozillahelper as well by adding a
cache, but the underlying issue should be properly fixed IMO.