The July 1st e-mail, posted on Mozilla's developer site, was penned under the name of Google engineer Fritz Schneider.
''I thought I'd drop you a note to give a heads up on something Google will be releasing next week: a version of our Internet Explorer toolbar for Firefox,'' the e-mail reads.
Schneider said the Firefox toolbar is slated for release on Thursday, July 7.
The e-mail also asks developers not to speak with the press until Google makes the announcement tomorrow.
The software will work on Microsoft's Windows 2000 and XP platforms, Mac OS X 10.2, and ''Linux 8.0+'', as well as quick links to Google properties and access to advanced functionality such as spellchecking and translation.
''It has pretty much the same features as the latest IE toolbar except of course for things like the popup blocker,'' the e-mail said. Firefox already has built-in Pop-up features.
Although Google's toolbar has been available for Internet Explorer (IE) for more than four years, this would be the first time the search giant moved to create a version for users of a browser developed by the Mozilla foundation.
The release of a Firefox version likely signals Google's growing awareness of increased market penetration by the open source browser. The once obscure browser continues to snatch users users from industry titan Microsoft's Internet Explorer.
Google and Microsoft's competitor Yahoo released a Firefox version of its own toolbar in February.
''We really appreciate the work you folks did to fill this gap in our products for so long,'' the Schneider e-mail said.
It also said the company would keep a link to the Googlebar from the toolbar download page so users can make the choice of which toolbar they'd like to install.
Google representatives were not immediately available for comment.
This article was first published on internetnews.com.