Rated 4 out of 5 stars

Now when this add-on works on Thunderbird 10 it is just great. Very useful!
However, I have two suggestions to make it even better:
1) The message box that appears and tells me in which folder the e-mail was filed is appearing in a very slow animation on the screen. It takes like 15-20 seconds for it to appear and disappear. (I have the taskbar at the left edge on the screen). While it is showing, I can't move e-mails through folders by hand in Thunderbird.
2) It would be great if the "%20" codes in the same message box were translated into spaces (and the same for other similar and common characters).
:)

This review is for a previous version of the add-on (0.6).  This user has other reviews of this add-on.

The notification uses the alert calls (https://developer.mozilla.org/en/XPCOM_Interface_Reference/nsIAlertsService)
The alert behavior is controlled by the alert.* preferences. They can be changed in about:config, but this will also influence the message notifications for your normal mail.
For the "%20" codes can you please file a bug at the support site (https://code.google.com/p/filemailextension/issues/list) with a screenshot.

Thanks