Its creator, Baydin, tells Mashable that the company became profitable for the first time last month, just before passing the 1-million-downloads mark.
The free inbox tool installs a button in Gmail from which users can schedule outgoing emails for optimal times or keep tabs on emails they receive. Instead of starring important emails, users can "Boomerang" them -- scheduling the emails to return as new messages at either a specific time or if nobody responds.
The Gmail extension launched in 2010 shortly after an Outlook version of the same tool, but it took off faster. Baydin CEO Alexander Moore says it hit 70,000 downloads within a week after launch, and its recent growth accelerated when the company started a promotion that rewards users for referring friends with the chance to win prizes such as T-shirts and Amazon Kindles.
Though most of the 1 million downloads of Boomerang for Gmail were free, Moore says that 10% of users opt to pay either $4.99 or $14.99 each month for access to premium features such as a mobile version, notes and the option to schedule recurring messages.
As email creeps further into our work days and holidays alike, Boomerang isn't the only inbox management tool that has taken off.
Email add-on Rapportive, which shows social data about contacts as you email them, was acquired by LinkedIn last month. Other email extensions that specialize in managing unruly inboxes include ToutApp, Xobni, Sanebox and Taskforce.
Moore says Baydin plans to build a suite of email extensions, the next of which will involve a calendar.
"Email is (and will continue to be) the medium where we share information-rich messages, coordinate schedules, and organize our priorities," he says. "That's why in the workplace email is more important than ever."