The Pebble app polls every 9 minutes and only sends notifications of unread messages. If you email yourself from various email clients to test the feature, be aware that it is possible your email client will mark a message read if its a message to yourself. Wait for an unread message to arrive to determine how things are working. Also, like Caller ID, the Pebble app is now handling email notifications. If iOS force quits the Pebble app, or you remove it yourself from running in the background, you won't get email notifications.