Network managers thinking about migrating their Internet e-mail servers from the popular open-source sendmail software to a new commercial version will find comfort in numbers. Officials at Sendmail Inc., an Emeryville, California start-up, say more than 1,600 customers, including Coca-Cola Enterprises and the Janus Funds Investment Firm, have made the switch.

Available for less than one year, Sendmail Inc.'s Unix and Windows NT server software products are used for Internet e-mail routing and hosting. Customers include large corporations such as Comdisco and Citicorp, government agencies such as the Federal Aviation Administration and the Internal Revenue Service, and electronic commerce companies such as Schwab online and BuyGolf.com.

One customer that made the move is Go America Communications, a nationwide wireless ISP in Hackensack, New Jersey. Go America used the public domain version of sendmail for four years before switching to Sendmail's commercial version a few months ago. Running Sendmail Pro on Solaris, Go America handles tens of thousands of internal and customer e-mail messages per day.

"We've had absolutely no problems," says Terrence Randell, assistant vice president for technical operations. "They've done a lot of work to create mechanisms to help stop spam and improve security -- features that were lacking in the public domain version."

"Our customer base proves that this model of building a commercial entity on open source software is a successful one," says Rich Guth, vice president of marketing at Sendmail Inc. Guth says enterprise customers often use the Unix-based Sendmail Pro package to route e-mail from the Internet to groupware packages, such as Microsoft Exchange, Lotus Notes and Novell GroupWise. Smaller companies tend to use Sendmail for NT to handle e-mail routing and hosting functions.

As a sign of its penetration of the e-mail market, Sendmail Inc. says its Unix and NT products will be integrated into six Internet applications: content management offerings from Brightmail and TrendMicro; unified messaging products from GFI and Iperia; and mass-mailing applications from Exactis and Boldfish. Still to come are partnerships in the areas of notice systems, e-mail response management and document management.

Developed in 1981 by researcher Eric Allman, sendmail is a public domain software package used on 75 percent of the world's Internet e-mail servers. Sendmail Inc. was formed last year by Allman to provide souped-up versions of the software and management tools to commercial customers.

"Everything I see Sendmail Inc. do is incrementally positive and is all in the right direction," says Eric Arnum, editor of Messaging Online.

Arnum says Sendmail Inc. is doing well against its competition, which includes other vendors of Simple Mail Transfer Protocol e-mail servers such as Ipswitch and Seattle Labs.

However, Arnum takes offense at Sendmail Inc.'s marketing strategy, which he says blurs the distinction between the number of users of its commercial software vs. the number of users of the public domain version of sendmail.

With regard to Sendmail Inc.'s new partnerships, Arnum says the company was smart to team with TrendMicro and Exactis, both of which have hot applications.