Rated 5 out of 5 stars
Very useful addon, I used it to import 23640 emails from windows mail! :)
Succesfully managed to import all emails in eml format without errors, also in subdirectories. Note that I did not import all emails at once, but always one major folder at the time.. in any case my biggest folder (sent items) counts approx 10600 emails! And I did not encounter problems.