The health effects of "threatening" e-mails sent by bosses to their workers has been revealed by researchers.
Aggressive email sent blood pressure soaring
Experts from Buckinghamshire Chilterns University College attached blood pressure monitors to volunteers before they opened their inboxes.
They found that blood pressure shot up if emails were from their superiors - or written in an aggressive tone.
Organisational psychologist Professor Cary Cooper said that e-mail should never be used to discipline staff.
There is evidence that, at least in the longer term, a raised blood pressure is harmful to health.
Whether or not brief rises, or even jobs with frequent stresses are harmful is far less clear.
However, the latest study, presented at a British Psychological Society Conference in Stratford-upon-Avon, is direct evidence of the power of a badly-worded e-mail to trigger physical changes.
A group of 48 volunteers had their blood pressure tested before and after they looked at a variety of e-mails, both from colleagues of equal status and those of higher status - and written in a neutral or aggressive tone.
Howard Taylor, one of the researchers, said: "Although participants' blood pressure rose to some degree after reading the threatening email and the e-mail from a superior, the highest increase was seen in those reading an e-mail which was both threatening and from a higher status colleague."
They concluded that it would be "counterproductive" for managers to write aggressively-worded e-mails to their staff.
Some companies have recently taken the step of banning the use of e-mail for internal communications between colleagues on the same site - claiming that it is fast becoming more of a burden to efficient working and teambuilding than a boon.
Professor Cooper, who lectures in organisational psychology at Lancaster University, told BBC News Online that face to face meetings were best for important instructions or news.
He said: "You should never hire or fire someone by e-mail - or choose this way to castigate them.
"Bosses only do it because they are too afraid to deliver the news face to face."
He said that while speaking to someone in person allowed vital non-verbal cues to be passed over which might soften the impact of a tough message from the boss, on e-mail, only the aggressive words remained.
He said: "E-mail is not a social support for us anymore - it's more like a source of stress.
"I once spoke to someone who said he was frightened to open his e-mail after two weeks' holiday."
The research was led by Dr George Fieldman.