Nextel Communications Inc. said yesterday it is offering a new service that allows its cell phone subscribers to record a voice message and send it to anyone with an e-mail address.

The service, called NextMail, builds on the Reston-based company's popular push-to-talk service, which allows Nextel users to radio each other by pressing a button on the side of the phone instead of dialing a seven- or 10-digit number.

The push-to-talk service is a lucrative one for Nextel, whose customers pay more per month on average than those of other cellular companies, in part because its business customers want the walkie-talkie feature. It is used by more than 90 percent of its 13.4 million subscribers, and Nextel recently launched an international version of the service through affiliates in Canada, Brazil, Argentina and Peru.

Rivals such as Verizon Wireless and Sprint Corp. have launched push-to-talk services, but Nextel became the first to market it a decade ago, and "we still consider ourselves to be the pioneers in the industry," said Cheryl Hawkins, a spokeswoman for Nextel.

The new $7.50-a-month service works using the same button. A subscriber must first enter e-mail addresses through Nextel's Web site. Then, to send a voice mail from the cell phone, the user selects the address or addresses on the phone screen and presses the button to record the voice mail, which is transmitted as an MP3 file to as many as 50 recipients at a time. "We look at it as an evolution of the push-to-talk service," Hawkins said.

Other cell phone companies allow users to send pictures and e-mails from cell phones, but Nextel is the first to offer voice mails through e-mail.

"It seems like a prudent way to mine new revenue out of existing customers," said Jonathan Atkin, an analyst with RBC Capital Markets. It's a novel idea, but it's not clear how much demand there will be for the added service, he said.

The Department of Justice has launched an antitrust investigation related to Nextel's walkie-talkie service that is still pending.