I misunderstood the cause of the slowness then, if it is really true that updating the index is not an important factor. I don't remember seeing profiling, but since I don't have any myself I'll take your word for it.
It always frustrates me to see people speculate on stuff instead of getting their stop watch out and trying it
Just get a small shell script to run `touch ${rand_file}` 35,000 times and time it. Then drop into your shell and do rm -rf on the folder (for bonus marks you could purge the disk cache before doing this). This gives you a benchmark on your hardware separately to what dovecot offers. Take that number and lets work from there... Shouldn't take too long to do something like this?
Ed W
