When it comes to work, email is both a blessing and a curse. Often, it feels like managing that constant flow of electronic messages is a job unto itself. An overflowing inbox is a constant frustration for Carol Burns, chief clinical dietician at Beth Israel Deaconess in Plymouth. "It's just when you set aside time to work on a project or do something, and instead, you are reading 37 emails about things that aren't that essential." By one estimate, as much as 28% of a worker's time on the job can now be consumed by email.