This will only work depending upon how your mail server is configured. If you have a Mail directory for each user, you should be able to follow these instructions in order to automatically send a reply to everyone who emails you, useful for notifications of being on holiday or out of the office.
Go into your mail folder and create a file called .procmailrc and then edit this file to contain the following:-
LOGFILE=$HOME/.procmaillog
VERBOSE=no
SHELL=/bin/sh
:0 c
* !^From +email@yourdomain.com
* !^Subject:.*Re:
* !^FROM_DAEMON
* !^X-Loop: email@yourdomain.com
* ^TOemail@yourdomain.com
| (formail -t -rI"From: fromaddress@yourdomain.com" \
-A"X-Loop: email@yourdomain.com" ; \
cat .vacation.txt) | \
/usr/sbin/sendmail -oi -t
Substitute email@yourdomain.com in the script above with the email address to which you want an auto-response made from.
The fromaddress@yourdomain.com in the formail line is optional and is the email address from which your auto-response message will come from. This is handy if you want a different email address to one you use regularly or don't want spammers picking up your real email address from auto-responses.
Next, you need to create the actual 'vacation' message that will be automatically sent to everyone who emails email@yourdomain.com - called .vacation.txt in the example above.
Create a new file called .vacation.txt containing something like the following text.
This is an auto-responder for <your name>'s email. I am out of the office and out of all email contact until ..... I will respond to your email on my return.
Now, whenever anyone emails email@yourdomain.com the mail will still be delivered to your mailbox and they will additionally receive an email containing the text in the .vacation.txt file
  |