An out-of-office reply that works

Watch it in a short film

Setting up an out-of-office message in webmail 1:03

Module 6: Automatic: filters and out-of-office · Reading time: 9 minutes

Learning objective: After this lesson you can explain how an out-of-office reply works on the server and who does and does not get it. You can also set up an out-of-office reply that switches itself on and off and reveals nothing that helps scammers.

Key concepts: out-of-office reply, Sieve vacation, Reply interval (:days), My e-mail addresses (:addresses), List-Id, Auto-Submitted, Start time and End time, Incoming message action

A filter that replies

Technically, an out-of-office reply is a filter. It sits in the same filter set as your other filters (lesson 6.1), so it also runs on the server at the moment mail arrives. Your laptop can be switched off. The Sieve extension is called vacation (RFC 5230). This is how the webmail writes an out-of-office reply for the Christmas holiday:

require ["date","relational","vacation"];
# rule:[Out of Office]
if allof (currentdate :zone "+0100" :value "ge" "date" "2026-12-21", currentdate :zone "+0100" :value "le" "date" "2027-01-03")
{
	vacation :days 7 :addresses ["emma@example.com","info@example.com"] :subject "Away until 3 January" "Thank you for your email. I am away until 3 January. For orders, please contact Tom: tom@example.com.";
}

What it says:

currentdate ... "ge" ... "2026-12-21" and "le" ... "2027-01-03": the current date must be on or after 21 December, and on or before 3 January. Those are your Start time and End time. Outside that period the filter does nothing. :zone "+0100" is the time zone from your settings.
vacation :days 7: the same address gets a reply at most once every 7 days.
:addresses [...]: the addresses that belong to you.
:subject and the text after it: the subject and body of the reply.

One reply per sender per interval

Without a limit, someone who emails you ten times would get the same reply ten times. That is why the server remembers who it has already replied to. Within the Reply interval (:days in Sieve), the same sender does not get a second reply. If you choose nothing, the standard sets it to 7 days (RFC 5230, section 4.1). For a two-week holiday, 7 is a fine value: anyone who emails you again after a week gets a reminder that you are still away. Shorter than 1 day is usually not possible.

The reply goes to the envelope sender (Return-Path, lesson 1.1), not necessarily to the address in From. For ordinary mail they are the same. For newsletters and systems it is often a technical address, and that is exactly the point: this way an automatic reply does not land with a person who can do nothing with it.

Who does not get a reply

An out-of-office reply can do a lot of damage if it replies to the wrong mail: replies to a mailing list with a thousand members, or two automatic messages endlessly responding to each other. That is why the standard (RFC 5230, section 4.6) says the server does not reply to:

mail with a List-Id header or other List headers: newsletters and mailing lists;
mail with an Auto-Submitted header with a value other than "no": automatic messages, such as another out-of-office reply or a system notification;
mail from addresses such as MAILER-DAEMON, or addresses that start with "owner-" or end in "-request".

Your own reply is given the header Auto-Submitted: auto-replied. That way another out-of-office reply knows it must not reply back, and no loop is created.

My e-mail addresses: replying only when it is meant for you

The server only replies if one of your addresses is in the To or Cc header (RFC 5230, section 4.5). This prevents replies to mail that arrived through a list or as Bcc. The server only half knows which addresses are yours: certainly your mailbox address, but not the info@ address that is forwarded to you.

That is why the My e-mail addresses field matters (:addresses in Sieve). Enter every address you receive mail on, including forwarding addresses. With Fill with all my addresses, the webmail copies the addresses of your identities. If you forget info@, a customer who emails info@ gets no out-of-office reply and may be waiting in vain.

Start, end and what happens to the mail

With a Start time and an End time, the reply switches itself on and off. That is the safest way: you cannot forget to switch it off. If you leave them empty, the reply stays active as long as Status is set to On. An out-of-office reply that keeps running for weeks after the holiday is a common mistake and confusing for customers.

Under Incoming message action you choose what happens to the mail itself. Leave this set to Keep. Vacation simply leaves the message in your mailbox (RFC 5230, section 4.7), and when you are back you want to read what came in. Discard means that mail you receive disappears. Redirect to or Send copy to only make sense towards a colleague in your own organisation, with the same drawbacks as in lesson 6.2.

The Out of Office section with Subject, Body, Start time, End time and Status — (1) Subject, (2) Body, (3) Start time and End time, (4) Status, (5) Reply interval

What to write and what not to write

A good out-of-office reply is short and helps the sender move on:

When you are back, or until when you will not reply.
Who is covering in the meantime, with an address or phone number that is staffed.
What the sender can do if it is urgent.

And what you do not write: details that help scammers and burglars. The reply goes to everyone who emails you, including spammers and strangers. So do not mention that you are abroad for three weeks, where you are going, your private number or the name of your stand-in together with a role a scammer could abuse ("email our bookkeeper John for payments"). Scammers love using a message like that to write a convincing fake email, for example an urgent payment request in the name of someone who cannot be reached anyway.

Example of a good reply:

Subject: Away until 3 January

Thank you for your email. I will be reading my mail again from 4 January.
For orders and questions, please contact info@example.com.

Not twice

You can also set up an out-of-office reply in your hosting control panel, which at WebOké is DirectAdmin. Use one of the two. If both are switched on, everyone gets two automatic replies.

In practice: how it works in the webmail

The out-of-office reply is under Settings > Out of Office, with Subject, Body, Start time, End time and Status, and under Advanced settings you find My e-mail addresses, Reply interval and Incoming message action. You can see the result in Filters > Actions > Edit filter set. The steps are in the Roundcube manual under Setting up an out-of-office reply. Other webmail works in a similar way: Gmail has a vacation responder in its settings, Outlook.com has automatic replies.

Summary

An out-of-office reply is a Sieve filter (vacation, RFC 5230) that runs on the server.
The same sender gets at most one reply per Reply interval; if you choose nothing, that is 7 days.
No replies to mailing lists (List-Id) or automatic mail (Auto-Submitted), and only when one of your addresses is in To or Cc.
Add your forwarding addresses under My e-mail addresses too, use a start and end date and leave the action set to Keep.
Write when you are back and who people can contact, but no details that help scammers.

Quiz

Exercise

Exercise A6.3: Have your out-of-office reply checked. In your own mailbox, prepare an out-of-office reply under Settings > Out of Office, with a Start time and an End time that are both in the future; that way the reply is not really active yet and nobody gets a reply now. Fill in a subject, a text, My e-mail addresses and a Reply interval, and leave Incoming message action set to Keep. Then paste your filter set (Settings > Filters > Actions > Edit filter set, copy everything) or upload the file from Download. The program reads the script in memory (nothing is stored) and checks: there is a vacation action; :days is at least 1; the subject is not empty; the text is longer than 40 characters; there is a date limit with currentdate (otherwise orange: will you remember to switch it off?); :addresses contains at least one address (otherwise orange); and the message is kept, so no discard and no redirect to an address outside your domain. Switch the reply off again after the exercise if you do not need it.

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