VSRE stands for “very short reply expected”. It’s a way for you to indicate to the recipients of your email that they have to reply with a short (usually one to five words) reply. Typical replies to VSRE are “Yes”, “No”, or “Tuesday”, or “Pls send more info". It is not a standard, just a human convention, like FYI, or RSVP. Why? We all get a ton of email. In most cases replying politely can be demanding.