VPOP3 has an autoresponder facility for sending automatic replies when a message arrives in a mailbox. This is often used for 'Out of Office' replies, but it is not limited to that use.
To set an autoresponder, the administrator can edit the user and go to the Autoresponder tab. Alternatively, the user can edit it themselves by going to their VPOP3 Webmail account and going to Tools → Autoresponder (Tools → Settings → Autoresponder in version 4).
Note that autoresponders only work when messages arrive in a mailbox. If you have forwarding, assistant, mappings or other rules set meaning that the message does not end up in the mailbox, then the autoresponder will not fire! If you want, the administrator can set the autoresponder not to keep the message after responding to it (the user can't do this themselves, as we have found that this leads to too many lost messages!)
So, for example, if you want messages to User1 to be forwarded to User2 and autoresponded to, you can set the autoresponder on User1, set it not to keep the messages, and set an Assistant to copy the message to User2 (do not check the Redirect to assistant box).
For more details see the reference guide
If you want to set a single autoresponder which replies to incoming messages for anyone (eg if your whole company closes for a holiday), you can obviously do this by going to each user and setting the autoresponder separately for each user.
If the autoresponder text will be the same for every user, and you have a spare user slot in your VPOP3 licence, there is an alternative way: