Sieve filters and vacation replies

Nixt Server runs each person’s own rules on the server, as mail is delivered, so they work whichever app — or no app — is open. Rules are written in Sieve, the standard language for mail filters, and managed over ManageSieve. Out-of-office replies can also be set from a JMAP app without writing any Sieve.

How rules run

• Each account can keep up to 32 Sieve scripts. One of them is active, and only the active script runs.
• The active script runs once for every message delivered to the account, after the server’s own spam and malware filtering has accepted it.
• Mail the filter tagged as junk or quarantined goes to Junk or Quarantine whatever the script says; the script’s other actions, such as flags and notifications, still apply.
• If the script does nothing that files or discards the message, the message is kept in Inbox.
• If the script fails while running — it goes over a limit, for example — the message is kept in Inbox and the failure is written to the server’s log.
• Scripts are checked when they are uploaded, so a script with a mistake is refused with the reason and its position rather than failing later.

A first script

require ["fileinto", "imap4flags", "vacation"];

# File mailing-list mail into its own folder, creating it if needed
if header :contains "list-id" "announce.example.org" {
    fileinto :create "Lists/Announce";
    stop;
}

# Flag mail from the boss
if address :is "from" "sam@example.com" {
    addflag "\\Flagged";
}

# Out of office
vacation :days 7 :subject "Away until Monday" "I am away and will reply when I am back.";

Upload it with any ManageSieve app, then make it active. See ManageSieve.

Supported extensions

Every script may require any of these. The ManageSieve SIEVE capability lists them, together with the comparators i;octet and i;ascii-casemap.

Notes on some extensions

• Folder names. fileinto "Receipts" files into a folder of that name. If it does not exist and :create is not given, the message goes to Inbox. fileinto :specialuse "\\Archive" "Archive" finds the folder by use first.
• Special uses available: \Drafts, \Sent, \Junk, \Trash and \Archive.
• redirect sends the message on to another address. A destination outside your organisation goes only once your organisation allows it: saving the script answers OK (WARNINGS) saying the forward waits for approval, and until then the message is kept in your mailbox (see Forwarding outside the organisation). The server rewrites the envelope sender so the destination’s SPF check sees this server’s domain. A redirect to the account’s own address is ignored. Without :copy, the message is not kept.
• reject and ereject keep the message out of the mailbox and send the sender a delivery failure notice carrying your reason, with status 550 5.7.1, when the sender asked for failure notices and passed SPF or DKIM.
• notify with a mailto: URI sends a short notification message from your address. A :from that is not one of your own addresses is set aside, and the notification comes from you, because the server signs the mail it sends in your domain’s name.
• include can include your own scripts (:personal).
• environment answers name, version, location and phase.
• date and currentdate use UTC when the script names no zone.
• duplicate remembers what it has seen for up to 30 days.

Limits

Limits the organisation sets

An organisation can set tighter limits on its people’s scripts in its runtime settings:

Each refusal names the setting that caused it in the message’s trace.

The organisation’s own rules

An organisation can run a Sieve script of its own before everybody’s and another after:

• Before runs first, on every message to the organisation’s people. What it decides stands: a discard, a reject or a stop there ends the run, and nothing a person’s own script does takes back what it filed.
• A person’s own script runs next, as ever.
• After runs last, on every message — one a person’s script rejected too — which is where an archive or journal copy goes. What it files stands, even over a person’s discard.

Each script sees the message as the one before left it, headers it edited included. A script that fails to run counts as having done nothing, so mail is never lost. The organisation’s redirects are its own forwards: they never wait for its approval of forwarding, and never count against a person’s limits.

For example, to keep a copy of every message in an archive:

require "copy";
redirect :copy "vault@archive.example";

Organisation administrators set them, and auditors read them:

• Console: Settings › Organisation rules.

• Command line:

  versealx-server admin scripts show
  versealx-server admin scripts set --after after.sieve
  versealx-server admin scripts set --no-after

• API: GET and PUT /api/v1/tenants/{tenant}/scripts, both saved whole with the version read.

A script that doesn’t compile is refused, naming the line and the column.

ManageSieve

ManageSieve is the protocol apps use to upload and choose scripts. Connect to the server’s host name on port 4190, start TLS with STARTTLS, and sign in with your email address and password.

Refusals are NO replies. The response code in brackets is what an app acts on; the text is what it can show you.

After several failed sign-ins on one connection, the server sends BYE "Too many failed authentications" and closes it.

Vacation replies

An out-of-office reply can come from two places:

If the active script runs a vacation action for a message, that reply is used and the JMAP setting is ignored for that message.

Setting a reply over JMAP

VacationResponse/set on the singleton object takes:

A JMAP reply goes to each sender at most once every 7 days. Nixt Mail’s out-of-office setting uses this; see the Nixt Mail documentation at /docs/mail.

Who gets a reply

For both kinds of reply, a message gets none when:

What the reply looks like

• From is your address, or the Sieve :from address when it is one of your own; any other :from is set aside. To is the sender.
• It is signed with your domain’s DKIM keys, so it passes DMARC where it lands. See Mail the server writes itself.
• Subject is the one you set, or Auto: and the original subject. A subject that is not plain ASCII is encoded so every mail app displays it correctly.
• In-Reply-To and References link it to the original, so it appears in the same conversation.
• Auto-Submitted: auto-replied and Precedence: bulk stop other servers’ auto-responders replying back.
• The envelope sender is empty, so the reply can never itself cause a bounce loop.