Earlier quoted context omitted.
I have to disagree: It may be legal and in your self interest, but I don't think you should reneg on your offer. You should treat others the way you want to be treated, which means honouring the email agreement. And if you do withdraw your offer to company x, don't complain if company y withdraws its offer to you. If you stick with company x then show them the job offer from company y at your next salary review. It i…
It is not usually the employee who sets the deadline on the offer, so I don't believe this moral equivalence is real. If a company does not want this situation to come up, it is at liberty to give a deadline that's long enough for the employee to consider other offers and make an informed decision. A company that attempts to rush an employee to accept an offer before others come in is attempting to exploit the employ…
(it's just as easy to assume the latter... that the first offer was accepted because it was perfectly reasonable and the second company was slow to make an offer and poor at communicating. If the second company did take a surprisingly long time to make an offer that's actually another variable to take into account; possibly representing organisational problems or a preference for other candidates at their end)