we can agree that a signed CO IS best, but I accept email acceptance for prop's/CO's for one particular commercial account with which I have a long standing good relationship. The difference in our situations may be that the commercial account is national and they have money set aside for the maintenance issues whereas if you're working for a GC who's balancing the balls for a HO w/ the funds, the GC may cut you off b/c of lack of funds at the final. My acceptance for the commercial account includes explicit wording; i.e. "I accept the proposal" is ok with the proposal at the bottom of the replied to email...."go for it" with the project name as the header does not cut it.
cover your butt and feed your family.
cover your butt and feed your family.