More than two-thirds of IT staff surveyed, 69%, admitted that they would open an e-mail they suspected to contain "inappropriate" material.
Corporate e-mail and internet use policies usually define "inappropriate" as the use and spread of pornography, racism, sexism and defamatory material.
NOP surveyed 100 professionals from each of the UK's largest employment sectors: accountancy, civil service, financial services, legal, retail, manufacturing and IT.
It found IT workers (42%) were most likely to circulate inappropriate material and second most likely (behind retail) to open suspect e-mail.
Despite this, 66% of IT workers surveyed said they understood that the e-mail they sent at work had the same legal status as a letter sent on a company letterhead. Some 60% told NOP they knew the potential damage to their career or reputation of a major e-mail blunder.
The NOP survey also showed that IT professionals find spam (21%) and racist content (20%) the most upsetting type of e-mail, ahead of pornography (14%) and negative remarks about colleagues or customers (8%).
Steve Purdham, the chief executive officer of SurfControl, the filtering and content management technology vendor which commissioned the research, said: "The results of the survey are startling. IT staff should know better."
Purdham called for a renewed effort from businesses to educate staff, backed by the deployment of filtering technologies to minimise corporate risk from staff e-mail abuse.
Last month CW360.com's sister magazine Personnel Today revealed that almost one in four employers have sacked staff for misusing the Internet. Of these dismissals, 69% were related to pornography.
For reader feedback on "inappropriate" use of the Web at work, check out Your Shout!