Technically they are not startups, but for for gmail you may want to have a look at Graph Your Inbox ( http://www.graphyourinbox.com/ http://www.graphyourinbox.

Technically they are not startups, but for for gmail you may want to have a look at Graph Your Inbox ( http://www.graphyourinbox.com/ http://www.graphyourinbox.com/ ) or Gmail Meter (http://gmailblog.blogspot.com/2012/04/know-your-gmail-stats-using-gmail-meter.html http://gmailblog.blogspot.com/2012/04/know-your-gmail-stats-...).