An auto-responder email is a an e-mail that is sent from your mailbox as the reply to each e-mail that you receive. The content is predefined and it is sent automatically, so every single person who contacts you via email will receive it once their email is received on the server that manages your emails. This feature is used when you need to inform people about different things, for example being out of the office for a given period of time or that an purchase is received and is currently being processed. The auto-responder email furthermore functions as a verification for those who get in touch with you that their message has been received, even if you are not able to read it and make contact with them at once. It can include virtually any text that you choose and also it can be modified based on the exact occasion.