Mr Justice Tugendhat rejected the defence that the email was protected by qualified privilege because it was part of a campaign ahead of an election for the trade body and awarded £30,000 in damages because of the seriousness of the allegation and the fact that the audience for it was made up of her professional peers.
"The allegation that a director has abused her position to prefer her private interests over her duties is a serious libel," he said in the ruling. "The publishees in this case were fellow members of her own profession. A professional person's reputation amongst colleagues is one of the most important considerations of such a person."
Jan Cambridge was an interpreter and a director on the board of trade body the National Register of Public Service Interpreters (NRPSI), which sold the rights to access its database of interpreters to the Cambridge Interpreting and Translation Agency (CINTRA).
Cambridge subsequently did work for CINTRA and fellow interpreter Guillermo Makin accused her of having "interests" in CINTRA when access to the database was sold to it, and of helping CINTRA, via NRPSI, to obtain a contract with police forces.
The email was sent to interpreters who were entitled to vote on an upcoming vote of no confidence; were members of the NRPSI or other trade bodies; or were commercially affected by the results of CINTRA's winning of contracts.
The High Court found that the claims made in the email were not true.
"The charge is that '[Cambridge] worked as a trainer for CINTRA at the time our data was sold'. That is not true," ruled Mr Justice Tugendhat. "[Cambridge] did not work as a trainer at the time the Licence was granted, or at any time when she intervened in the discussions leading up to the grant of the Licence."
"On the true facts, as I find them, a reasonable man looking at the relevant facts and circumstances of the particular case would not think that there was a real sensible possibility of conflict," he said.
The ruling also said that the email's claim that there was evidence that Cambridge used her influence to help CINTRA win contracts.
Makin argued that the email was covered by qualified privilege because it was sent to members of a trade body before a vote and was part of a necessary democratic process.
Mr Justice Tugendhat said, though, that this did not apply to the people who were emailed who were not due to participate in the vote.
"There was in my judgment no duty on the part of [Makin] to publish the charge which [Cambridge] complains of to those who did not have a right to vote at the AGM, and such people had no interest in receiving that publication," he said. "It was simply an accusation made ... without any proper factual basis, and without any inquiry and without giving [Cambridge] the opportunity to rebut it."
In relation to those who did have an interest in the vote of confidence, Cambridge claimed that the comments were malicious, that Makin made the allegations without believing them himself.
"His motive, it is said, was to open the way for election to the Board of NRPSI of himself and those who shared his views on policy. It is said that as the date of the AGM approached, he lost any remaining sense of propriety and honesty in his determination to achieve his ends," said the ruling.
"I conclude that the Defendant did not believe the allegation complained of to be true. He did not care whether it was true or false," said the judge. "It follows that the publication to the members of CIOL was not on occasion of qualified privilege."
The High Court found that the message had serious implications for Cambridge. "Following the e-mails published by [Makin] in the Spring of 2007, persons with whom she was working ceased to be cordial and pleasant as they had been before, and stopped speaking to her," said the ruling. "Others demanded that she defend herself from the charges of wrongdoing made by the Defendant. Interpreters expressed their belief that she had caused destitution amongst them by her illegal acts."
The Court awarded Cambridge £30,000 in damages. She had previously reached a settlement of £30,000 with trade union GMB, through which Makin conducted some of his campaign through the union.