Cyrus Sieve

Introduction

Cyrus Sieve is an implementation of the Sieve mail filtering language ( RFC 3028 ). It allows a series of tests to be applied against an incoming message, with actions to take place if there is a match.

Mail filtering occurs on delivery of the message (within lmtpd).

Cyrus compiles sieve scripts to bytecode to reduce the overhead of parsing the scripts fully inside of lmtpd. This occurs automatically if sieveshell(1) is used to place the scripts on the server.

Sieve scripts can be placed either by the timsieved(8) daemon (implementing the ManageSieve protocol RFC 5804; this is the preferred options since it allows for syntax checking) or in the user's home directory as a .sieve file.

Installing Sieve

This section assumes that you compiled Cyrus with sieve support. If you specified --disable-sieve when running ./configure, you did NOT compile the server with sieve support.

Configure sieve

Depending on what's in your /etc/services file, sieve will usually be set to listen on port 2000 (old convention) or port 4190 (as specified by RFC 5804).

Add lines to the SERVICES section of cyrus.conf(5) to make the server listen to the right ports for sieveshell commands:

sieve         cmd="timsieved" listen="servername:sieve" prefork=0
managesieve   cmd="timsieved" listen="servername:4190" prefork=0

Sieve scripts are stored in the directory hierarchy specified by the sievedir imapd.conf(5) option (default: /usr/sieve). This directory must exist and be writeable by the cyrus user for timsieved to function, so organise that now.

Configure outgoing mail

Some Sieve actions (redirect, vacation) can send outgoing mail.

You'll need to make sure that lmtpd can send outgoing messages. Currently, it invokes /usr/lib/sendmail by default to send messages. Change this by adding a line like:

sendmail: /usr/sbin/sendmail

in your imapd.conf(5). If you're using Postfix or another MTA, make sure that the sendmail referenced in "/etc/imapd.conf" is Sendmail-compatible.

Managing Sieve Scripts

Since Cyrus is based around the concept of a sealed-server, the normal way for users to manipulate Sieve scripts is through the sieveshell(1) utility, in communication with the timsieved(8) service.

If, for some reason, you do have user home directories on the server, you can use the sieveusehomedir option in imapd.conf(5) and have the sieve script stored in the home directory of the user as ~/.sieve.

Sieve scripts in shared folders

Cyrus has two types of repositories where Sieve scripts can live:

  1. Personal is per user and

  2. Global is for every user. Global scripts aren't applied on incoming messages by default: users must include them in their scripts. Note that there are two types of Global scripts: global and global per domain.

When you log into Cyrus IMAP with sieveshell(1) you have the following combinations (Assuming there is manager and manager@example.com as admin in imapd.conf(5)):

  • sieveshell -a manager -u manager localhost - To edit global scripts.

  • sieveshell -a manager@example.com -u manager@example.com localhost - To edit global script of example.com domain.

  • sieveshell -a user@example.com -u user@example.com localhost - To edit personal scripts of some user.

Scripts for shared folders work different from user scripts. The last ones are loaded to the user's repository and attached to the inbox when activated. The first ones must be loaded to the global domain repository and attached to a shared folder by a user that has permission on it. Use the second combination listed above to load them and cyradm (or another compatible client) to do the attach:

sieveshell -u manager@example.com -a manager@example.com localhost
> put /tmp/my_script my_script
cyradm -u user@example.com localhost
localhost.localdomain> mboxcfg shared.folder@example.com sieve my_script

Testing the sieve server

The Sieve server, timsieved(8), is used for transporting user Sieve scripts to the sealed IMAP server. It is incompatible with the sieveusehomedir option. It is named after the principal author, Tim Martin, who desperately wanted something named after him in the Cyrus distribution.

From your normal account, telnet to the sieve port on the server you're setting up:

telnet servername sieve

If your server is running, you'll get a message similar to the following one:

Trying 128.2.10.192...
Connected to servername.domain.tld.
Escape character is '^]'.
"IMPLEMENTATION" "Cyrus timsieved v1.1.0"
"SASL" "ANONYMOUS PLAIN KERBEROS_V4 GSSAPI"
"SIEVE" "fileinto reject envelope vacation imapflags notify subaddress regex"
OK

Any message other than one similar to the one above means there is a problem. Make sure all of authentication methods you wish to support are listed. This list should be identical to the one listed by "imapd" earlier. Next terminate the connection, by typing:

logout

Next test authenticating to the sieve server. To do this run the sieveshell(1) utility. You must specify the server. If you run this utility from a different machine without the "sieve" entry in "/etc/services", port 2000 will be used.

sieveshell servername
Please enter your password: ******
> quit

This should produce the message "Authentication failed" with a description of the failure if there was a problem.

Next you should attempt to place a sieve script on the server. To do this create a file named myscript.script with the following lines. Replace "foo@example.org" with an email address you can send mail from, but that is not the one you are working on now.

require ["reject","fileinto"];
if address :is :all "From" "foo@example.org"
{
    reject "testing";
}

To place this script on the server run the following command:

sieveshell servername
Please enter your password: ******
> put myscript.script
> activate myscript
> quit

This should place your script on the server and make it the active script.

Test that the sieve script is actually run. Send a message to the address you're working on from the address mentioned in the sieve script. The message should be rejected.

When you're done, don't forget to delete your testing script:

sieveshell servername
Please enter your password: ******
> delete myscript.script
> quit

Cyrus Sieve Support

Special use folders

Some mail clients allow users to rename the system folders, such as Archive and Trash. This can make sieve scripts break if they are using folder names explicitly. Fortunately such folders have a special use flag, allowing you to access them from sieve without needing to know their current titles.

  • \Archive

  • \Drafts

  • \Junk - also known as the Spam folder

  • \Sent

  • \Trash

Supported extensions

Sieve has a lot of extensions. Cyrus supports a subset of these:

Note that the final RFCs of these last sieve extensions have significant changes that are not currently supported.

Sieve Tools

  • timsieved(8) - server side daemon to accept requests from sieveshell

  • sievec(8) - compile a script into bytecode. See sieved.

  • sieved(8) - decompile a script back from bytecode. See sievec.

  • masssievec(8) - compiles all the scripts in sievedir from imapd.conf.

  • sivtest(1) - authenticate and test against a MANAGESIEVE server such as timsieved.

  • sieveshell(1) - allow users to manage scripts on a remote server, via MANAGESIEVE

  • translatesieve(8) - utility script to translate sieve scripts to use unixhierarchysep and/or altnamespace

Writing Sieve

Sieve scripts can be used to automatically delete or forward messages; to send autoreplies; to sort them in folders; to mark messages as read or flagged; to test messages for spam or viruses; or to reject messages at or after delivery. Sieve.info has more information on sieve and its uses.

There's a good sieve reference online which describes the language.

For those who prefer a client to write code in, Sieve.info has a list of desktop, web and command line clients.