An email promoting a tango concert set off howls of protest in offices across Washington on Tuesday as recipients seeking to unsubscribe were hit by a flood of further unsolicited messages.

It started innocuously enough with an email from the Pan Am Symphony Orchestra to a list of email addresses in the Washington area announcing a March 1 concert of tango music.

As with many promotional emails, appended to the bottom of the message was the option to "unsubscribe" from the list.

As user after user, however, asked that they be removed from the Pan Am Symphony email list, their request was sent to all of the other recipients on the list.

It was not immediately clear if this was because they were also hitting the "reply to all" button or if the unsubscribe request was looping the email back to all of the members of the list.

Lawyers, lobbyists, journalists, defense contractors and think-tank members were among those demanding with increasing indignation that they be removed from the list.

"This is a US government agency -- remove this address from your records," said one message from a Federal Trade Commission attorney.

"It would be great if these unsubscribe messages did not copy every one else on the distribution," wrote another recipient.

An Agence France-Presse reporter received more than 100 unsubscribe messages from other users over the course of a few hours.

One recipient had a proposal for their new "friends."

"This has been great. Do you guys all want to get together for a drink?"