You can use one of the following links, to get more informations about this plugin:
All information about powermail developing, the developers behind powermail, time tracks and so on: https://github.com/einpraegsam/powermail
powermail is powered by http://www.in2code.de/
Do you need help from the community: http://www.typo3.net/
Don't miss the best TYPO3 blogging page: http://www.typo3blogger.de/
Did you see some helping information on http://www.youtube.com/ => search for “powermail”