Never include a cover letter that says something like
Here is my news release. We're excited about this product, and we're sure that your readers will be excited, too. We'd be happy to answer any questions that you may have about our new software.
This example covers about 100 percent of all press release cover letters that I've seen in my 29 years in the software development industry.
If there's information about your application that you want to include in the cover letter - information that explains the press release, then delete the cover letter, and include the information in the body of the press release.
Press releases are the path to the lucrative US and European software markets - if they're done properly. Don't personalize the news release that you send to the bloggers, magazines, and newspapers. It's unprofessional. The editors know that even the simplest email client can perform email-merges, and they're not impressed by a "Dear Sam:" salutation.
Talk to a press release pro, and send your press release in the format that editors will respect.