> Like, I wouldn't imagine you could send an email along the lines of, "Hey, I'm looking to buy some securities. You in, bro? DISCLAIMER: This is not an offer to buy or sell securities."

With the disclaimer, I expect this would be read as an "offer to treat". Not a contract offer, but rather, an invitation to negotiate one.

Coupons printed in the newspaper are also mere offers to treat, which is why they can be dishonoured.

Of course, I am not a lawyer, and this is not legal advice.

Everything gets tested at the extremes, but for the most part, email disclaimers are there as minor CYA measures for the sender of the email. Lawyers use them all the time, for instance, so that nobody misinterprets their daily chatter or off-the-cuff advice as constituting an official attorney-client relationship with the recipient.

Obviously you can't hide behind an email disclaimer to C your A if your A is blatantly violating the letter or spirit of the disclaimer.

Your specific example doesn't read to me like subterfuge at all. It looks to me like an informal discussion which may lead to a purchase of securities. After you say "yes" via email, we will probably construct an actual contract specifying details.

The disclaimer makes certain that both you and I realize this isn't an offer, just a conversation.

You might get into trouble if you routinely engaged in securities transactions via email with such a disclaimer. But if you handle all actual trades with a legalistic form containing no disclaimer, and informal conversations in email with a disclaimer, the disclaimer is likely to hold up in court.