Lets not send the lynch mob out yet. The A'gon community is very tight knit indeed, and he's quite likely to send the check back as promised. Djjd did a nice job on the legal end of it, but I don't suspect you want to fight this one... unless it is one special amp at one special price then just put you money back in your pocket and look for another one!
I'm a lawyer but will refrain from giving a detailed legal opinion at this time. Should the need arise, I'd be happy to help out Alexone in private emails without charging any fee. Believe it or not, we're not all crooks!
Suffice it to say that most courts would treat email correspondence for online transactions as meeting the writing requirement under the Statute of Frauds (in this case if it's a sale of goods for $500 or more, there must be a writing signed by the party to be held). Obviously, a "signature" is impossible to "prove" in standard email communication, but based on facts and circumstances, it wouldn't be difficult to establish that the emails were the product of your seller's mind and imagination and were not written by his cat, for instance!
Normally, the buyer's payment would be effective as an acceptance of the offer upon dispatching the letter under the "mail box" rule - unless, of course, a specific method of dispatch was agreed upon between the parties but then not followed by the buyer. Say, for instance, you agreed to send the money order by FedEx overnight (which I always do as a buyer) but then sent it by regular (snail) mail. In such a case, your acceptance would not be effective until receipt by the seller and he would have the right to revoke his offer in the meantime. This is one good reason to use overnight services unless it's a small transaction for less than $100 or so. Another good reason is to give proper respect to the nature of the transaction such that the seller will never be left waiting in suspense.
Negative feedback is a must in this instance. If he then retaliates with negative feedback for you, send a note to Cornfedboy asking him to look into the matter. I'm sure there is a way for A'gon to remove negative feedback if it's clearly unjustified. If worse comes to worse, then start another thread about it!
