Legal Question in Business Law in California

Maybe. This area of contract law is often discussed under the general heading of "silence as assent" and a frequent example is when someone makes an offer to enter into a contract, and the issue arises whether failure to respond with "No thanks" is the same as saying "OK." The law is that silence does NOT usually imply acceptance. If it did, we would be spending all day sending "No thanks" messages in response to e-mails, telephone messages, junk mail, and so on. However, there are limited situations in which silence is considered assent.....usually where the parties have a pre-existing business relationship or the customs of a particular business point in that direction.

There is another example. If you have an account with a merchant, repairman, medical service provider, or the like, where you get regular bills, failure to dispute a billing may, in time, ripen into an acceptance of the charges as billed (called "account stated" or "book account" depending upon the circumstances).

Despite the foregoing examples and the possibility of other, similar, situations, I would have to say that more often than not failure to respond to a received e-mail probably would not be deemed agreement with the matters proposed, stated or discussed therein.

Under some circumstances, silence can be evidence -- but not conclusive proof -- of agreement with someone else's statement. Since you haven't told us anything about your situation, I have no idea whether such circumstances might be present.