The short history of email disclaimers

October 15, 2013, 6:31 PM UTC

FORTUNE — Does your email have a tail? That cautious, or cautionary, language at the end of a message alerting recipients that the tax advice expressed within must not be used to evade taxes; or that the personal views are not the views of the company; or that the information is privileged, confidential, and should be returned to sender and deleted?

Boilerplate disclaimers are used not just by lawyers, but also by bankers, consultants, and even media organizations like The Economist Group. Last year, the Wall Street Journal called out an investment bank research firm for a disclaimer that was more than 2,500 words long.

How did this come to pass? How did our email addenda grow so ridiculous?

Though there’s little case law that addresses the email disclaimer, lawyers who have studied the matter (and who themselves use email disclaimers) say the disclaimer is both increasingly common and fairly useless. There are exceptions — on tax advice, a disclaimer is mandated by IRS Circular 230 — but on the whole, they ain’t worth much. John Hutchins, a partner at Troutman Sanders, says they are usually redundant, “kind of like a belt with suspenders.”

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A better analogy might be suspenders with no pants. Many disclaimers — particularly of the “This is confidential. Do not forward. Delete and return to sender” variety — are simply one-sided contracts. Without prior agreement from the other side, they’re unenforceable.

“If you send something without a confidentiality agreement already in place, you can’t say, ‘Oh, you’re bound by my little disclaimer at the bottom of my email.’ From a contract perspective it just doesn’t work,” Hutchins says. He compares them to “shrinkwrap agreements,” or terms and conditions agreements that cannot be read until after purchasing and opening a product — like software back when it was bought in a box — which courts have voided.

Several years ago, New York Times reporter Alex Berenson figured as much when he received an email from a lawyer that had been intended for another lawyer, Brad Berenson. The email was somewhat sensitive, regarding settlement negotiations of an investigation brought against drug maker Eli Lilly. Reporter Berenson was covering Eli Lilly’s legal troubles, and though he says he already knew the information contained in the email, he was not moved by the boilerplate language to destroy the email as demanded.

If disclaimers are toothless, why use them? Within the legal profession, they make some sense. Lawyers have an ethical duty to protect client confidences. This means both alerting the recipient that content is privileged, and more or less abiding by email disclaimers that assert confidentiality. (The specifics vary state by state — in some, lawyers are required to destroy an inadvertently received email protected by client privilege; in others they may just have to notify the sender). The email disclaimer, in fact, was a natural evolution for the legal universe: Lawyers include similar language in the form of a legend on top of paper documents and fax cover sheets. Lawrence Spiegel, a partner and general counsel at Skadden Arps, notes that to not include a disclaimer of this sort — particularly when all other firms do — could be considered a breach of that ethical duty.

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But in those less modern forms, disclaimers were used selectively and genuinely. With email, they are often attached regardless of content, a fact that Spiegel and others say can undermine whatever standing they may have. Disclaimers also tend to be appended to the bottom of emails, making the “do not read” clause preposterous. (Scott Talkov, a lawyer with Reid & Hellyer, advises attorneys to append the disclaimer at the top of an email.)

Spiegel doubts placement of the disclaimer matters but says in general: “They’re weakest when you need the other side’s agreement. Where they’re strongest is when they put the recipient on notice so they don’t have a misunderstanding or strategically seek to claim a misunderstanding which could have legal consequences.” For example, courts have enforced disclaimers that assert any deal agreed upon in email is not binding without a written contract.

But, even when they’re only giving notice, disclaimers are not foolproof. Talkov pointed me to Romero v. Romero, a case from 2011 involving feuding family members in California, one of whom sent an email declaring “payback is a bitch” and that email recipients “still have a gigantic debt to pay to me, which will be paid no matter what.” The e-mailer signed off “Your most determined, unstoppable, and visceral enemy,” and then appended a homemade disclaimer reading:

“DISCLAIMER: Not one word herein should be construed by anyone as meaning violent or threatening intentions, and instead the entire contents is to be taken by the strict literary meaning. There have not been, and will be any elucidated threats of violence or intent, either expressed or implied, within the entirety of this document.”

A judge did not find it compelling and issued a protective order.

As for the latest, most fashionable form of email disclaimer — “Sent from my iPhone, please excuse the typos” and its many other derivations — it works! According to a study from Stanford, messages that include errors are perceived to be far more credible when a mobile device disclaimer is attached.