The error apparently occurred when a MySQL employee mistakenly pasted the e-mail addresses into the body of the e-mail as a message, rather than placing the addresses into the recipient address box on the e-mail form.

In a statement today, the company acknowledged that "on Tuesday evening, a new MySQL employee accidentally sent out a promotional e-mail that contained the private e-mails of a small percentage of our users. We deeply regret this occurrence and are working on a stricter process to prevent this from happening again in the future. MySQL AB takes its privacy policy and the privacy of its users very seriously."

The vendor today sent out an e-mail to all 9,300 affected users to apologize and explain what happened, according to the company.

One MySQL user, Robert Brown, an IT project manager and consultant in Hackettstown, N.J., said he received the errant MySQL e-mail late Wednesday and was flabbergasted to find all the e-mail addresses -- including his own -- embedded in the message. "I can understand a user error, you know, 100 or 200 addresses," Brown said, "but more than 9,000? Come on."

Brown said he was so upset that he called the company to complain and find out what had happened. "My concern is that they're not being careful with e-mail addresses," he said.