An autoresponder replies automatically to mail arriving at an address. Used for a holiday notice or an acknowledgement that a message was received, it is genuinely useful. Configured carelessly, it replies to spam, argues with other autoresponders, and tells the internet you are away from home.
Setting one up
In cPanel, open Autoresponders and add one.
Email is the address that will reply. From and Subject appear on the reply; a subject like "Out of office until 3 September" is more useful than "Re: your message", because many people never open the body.
Interval is the hours before the same sender gets another copy. The default of 24 hours is sensible; setting it to 0 means every message gets a reply, which turns a conversation into a stream of identical notices.
Start and stop are the two fields worth using. Set both when you create it.
Set a stop time, always
An autoresponder with no end date runs until someone remembers to remove it. Everyone forgets.
The result is a company still telling correspondents it is closed for Christmas in March. It is a small thing that reads as a business nobody is paying attention to.
Set the stop date when you create it. If plans change, extending it takes ten seconds; noticing an expired one you forgot takes months.
Write it as though it is public
The reply goes to everyone who writes to the address, including spam senders, and anyone who guessed the address to see what comes back.
So "I am abroad until the 14th and the house is empty" is information you have just published. So are colleagues' direct numbers, if they did not agree to be listed.
A useful out-of-office says when you are back, who to contact if it is urgent, and that the message will be read on your return. That is enough, and it gives away nothing.
Loops between autoresponders
Two autoresponders replying to each other is the classic failure, and it produces a genuinely large number of messages quickly.
The interval setting limits it: with 24 hours, each side replies to the other once per day rather than continuously. That is the main reason not to set the interval to 0.
Mail servers also detect obvious loops and stop, but do not rely on it. If you run autoresponders on several addresses in the same organisation, be aware that internal mail between them can trigger both.
Do not autorespond on a public address
An autoresponder on info@ or sales@ replies to every piece of spam that address receives, which is a great deal of mail sent to addresses you do not control.
Two consequences. Your server sends a large volume of replies to forged addresses, which harms its sending reputation and can get the address blocklisted. And you have confirmed to a spam sender that the address is live and monitored, which is exactly what they were testing for.
Keep autoresponders on personal addresses where the volume of unsolicited mail is lower, and use a proper helpdesk for acknowledging mail to public addresses.
When a helpdesk is the right answer instead
If you want every incoming message acknowledged with a reference number and tracked to resolution, that is a helpdesk instead of an autoresponder.
An autoresponder replies and forgets. It cannot tell a first message from a follow-up, cannot include a ticket reference, and cannot stop replying once someone has answered properly.
For a support address receiving real volume, an autoresponder creates the impression of a system without any of the substance.
Removing one
Delete it from the same screen. The change is immediate.
Worth checking the list periodically rather than only when you remember. Autoresponders set up by someone who has since left are common, and they keep replying in that person's name indefinitely, which looks considerably worse than no reply at all.
If the person has left, converting their address to a forwarder pointing at whoever took over is the better arrangement. Setting up email forwarders picks it up from there.
If replies are not being sent
Check that the start time has passed and the stop time has not. Both are in the server's timezone, not yours, which is the usual explanation for an autoresponder that seems inactive on the day it was supposed to begin.
Check that the mailbox is not over quota. A full mailbox rejects incoming mail, so nothing arrives for the autoresponder to reply to.
And test from an external address rather than another mailbox on the same domain, since some server configurations skip autoresponders for local mail.
Say when the message will stop
An automatic reply that does not state a return date is less useful than one that does, and it is the single most common omission. Include when you will be back, who to contact meanwhile, and whether the message is being read at all. The last point matters most, since a reply saying somebody will respond shortly, sent by a mailbox nobody is monitoring, is worse than no reply. Set an end date on the responder itself where the system allows it, because the one left running after a return is a recurring embarrassment.