The 'autoreply' program lets you define an email alias which will automatically send a response to any email received by the alias.
The 'autoreply' program is preinstalled; therefore, the only steps you need to take are to create the text file for your reply, define the appropriate aliases in /etc/mail/aliases, and then run the mailctl restart command to reload the aliases file.
An autoresponder consists of two components: a reply message, which is automatically returned to the original sender, and the autoresponder itself, which triggers the reply message. Unless the autoresponder is for "information only," the original message is forwarded to the proper recipient as defined in the email aliases file.