This is what was originally posted:
i agreed to sell the name for two grand
The material terms of a sale contract are (a) what is for sale, and (b) what is the price. All other terms related to performance are determined by reasonable practice, but (a) and (b) are the only material terms.
Your apparent belief that a contract is formed only when someone signs a written document is outright wrong. The vast majority of all legal, enforcible contracts do not involve a signed writing of any kind.
And, oh yes, the "mendacious self-serving lawyer" crap surfaces yet again. Yah, I make a fortune commenting for free on forums. But, lawyers don't make any money when people agree and perform their agreements. In your vocabulary, saying "I agreed" means something peculiar - along the lines of "I didn't agree". Now, you either agreed or didn't agree to sell this domain name, but in your first post, you said "I agreed". Remind me not to "agree" with you in the future.
Can a contract be formed in an email exchange? Certainly it can. They wrote to someone whom they believed had authority over the domain. The person who wrote back agreed to sell the domain for 2K. In fact, you admit that person was you. Your point about whether they can prove it was you is an issue of evidence, not one of what the underlying truth was. Yes, if you proceed to deny it was you - i.e. lie - then I guess they'll have to check the IP address in the Yahoo email header and track you down in order to show that, yes, it was you and, yes, you are a liar. But saying, "they can't prove it was me" does not change the fact that it was, indeed, you who did the "agree"ing that you admitted in your first post.
The principle you are driving at - that there were things you didn't know when you made the deal - are relevant to the defense of contract non-performance known as "mistake". However, your argument has a long history of being defeated. A "mistake" worthy of dismissing non-performance is a mistake relating to the material terms - in this instance that you were mistaken as to (a) the domain, or (b) the price to which you "agreed" (I'll use quotes there, in view of your own personal definition of what it means to "agree". Under the law of contracts, it is never, never a "mistake" that you didn't know you could squeeze more cash out of the other party if you knew more about them. It just does not work that way. It is not a moral issue, but simply a black letter principle of contract law that has evolved over hundreds of years of commercial behavior.
What you came here asking is, "What is the most graceful way of breaching an agreement I made?" The fact that you are likely to find extremely little sympathy in this audience is a tribute to the rules of everyday contract law that this audience has internalized.
