SAN FRANCISCO (AFP) - Google on Tuesday added an embarrassment-avoidance tool that catches misdirected Gmail messages before they are fired off by users of the free Web-based email service.

A feature playfully dubbed "Got the wrong Bob?" is designed to warn people if it appears they may be about to send a Gmail message to an unintended recipient, according to Google engineers Ari Leichtberg and Yossi Matias.

"When's the last time you got an email from a stranger asking, 'Are you sure you meant to send this to me?' and promptly realized that you didn't?" Leichtberg and Matias asked in a joint blog post.

"Sometimes these little mistakes are actually quite painful. Hate mail about your boss to your boss? Personal info to some random guy named Bob instead of Bob the HR rep? Doh!"

The new feature from Google Labs can be turned on by modifying Gmail Settings. The software identifies groups of people Gmail users most often send messages to, and then alerts senders when they deviate from patterns.

"Gmail will try to identify when you've accidentally included the wrong person, before it's too late," the engineers said.

In the spirit of the new tool, Google has renamed a "Suggest more recipients" feature to "Don't forget Bob."

Gmail goof-prevention tools include "Undo Send" that recalls freshly sent email messages and "Mail Goggles" intended to thwart drunken messaging by only sending late-night emails after basic math problems are correctly answered.