NOTE: This extension/patch is no longer needed. The latest powermail already supports jQuery. So let us enjoy :)
For old versions, you may still use this, I however do not recommend this, instead it is time to update powermail to latest version.
Description of Powrermail Jquery:
Automatically adds support for jQuery when using powermail 1.5.6 and above.
This extension basically uses the following patch by Artem Matevosyan:
Credit goes to Artem Matevosyan for providing a patch that works perfect.