The Pew Research Center found 61 percent of those surveyed cited email as "very important" for their jobs and 54 percent said the same for the Internet.
The figures were even higher for office-based workers.
More than one in three surveyed said the landline phone was an important tool for work, compared with 24 per cent for a mobile or smartphone.
And despite the rise of social networks like Facebook and Twitter, just four per cent in the survey said these platforms were important for the workplace.
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"Email has proven its worth on the job as the foundational 'social media' day by day even as rival technologies arise.
"It was the killer app 45 years ago for the early Arpanet and it continues to rule workplaces despite threats like spam and phishing and competitors like social networking and texting."
Contrary to concerns that technology is a distraction, the survey found 46 per cent said digital tools made them more productive, compared with seven percent who said their productivity fell.
But one in three said the new landscape increased the time they spent working.
The importance of email in the workplace has been documented for some time. In 2002, Pew Research Internet surveys showed that 61 per cent of American workers were using email at work and in 2008, reported that 62 per cent of working US adults were "networked," meaning they used the Internet or email in the workplace.