Think before you send, the golden rule of email

But an email, hastily sent, can destroy your career, wreck a relationship and make you a laughing stock.

And that is why we need netiquette, according to the authors of a guide to good email manners.

The book explains some of the dos and don'ts of electronic messaging – reminding readers that anything you commit to email could be shared with thousands.

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It advises us to think carefully before pressing the send button. And only send messages you would be happy to receive.

Will Schwalbe, the book's co-author, said: "The thing that can send an important business relationship or a lifelong friendship down the tubes, could be as simple as one insufficiently warm email."

Research has shown that we send more emails than we make telephone calls.

One in six of us uses email to communicate – which means two million messages are sent worldwide every second.

But it is easy for them to come across the wrong way. For instance, "When words are written in capital letters, it means the writer is shouting at you," the book says.

Congratulations are an exception. "No- one minds 'HOORAY' OR 'CONGRATULATIONS' in capitals."

However, it is better to write Hooray!! than Hooray, because "email has a dulling quality that almost necessitates kicking everything up a notch just to bring it to where it would normally be". Ultimately the authors hope that better writing will mean fewer emails.

For example, if you write an email saying, "thank Janet" and the recipient has to write back asking "who is Janet?", this creates excessive messaging.

The book's advice might have been of benefit to Richard Phillips, of the law firm Baker & McKenzie. He sent his secretary an email asking for £4 for dry-cleaning after she accidentally spilt ketchup on his trousers.

Her response, which she forwarded to colleagues, mentioned that her mother had suddenly died.

She added: "Obviously your financial need as a financial associate is greater than mine as a mere secretary". The message was circulated worldwide.

And perhaps Joseph Dobbie, a web designer from Berkshire, should have thought of the consequences before he emailed a love note to a woman he had met saying: "Your smile is the freshest of my special memories. I will keep it with me when I need to find a smile of my own."

Paul Bogaards, of publisher Knopf, said: "We've arrived at a juncture in our civilisation where there is a clear need for this book. People need to master email or they become its slave."

Send: The How, Why, When – and When Not – of Email was a bestseller within 48 hours of publication in the U.S. It is due in the UK next month.