Sieve Troubleshooting

This page explains how to approach problems with Sieve.

Common Problems

Common configuration problems and their solutions are described here.

Sieve Scripts are not Executed

When Sieve scripts are not being executed, there are several possibilities:

Your MTA is not using Dovecot LDA or LMTP

Sieve scripts are executed by the Dovecot LDA and/or the Dovecot LMTP Server service. Thus, you first need to check whether LDA or LMTP are actually being used.

At least one of these is supposed to be called/accessed from your MTA e.g. Exim or Postfix, for local message delivery. Most MTAs have their own local delivery agent, and without explicit configuration this is what is used. In that case, your Sieve scripts are simply ignored.

When you set log_debug = category=sieve in your configuration, your logs will show details of LDA and/or LMTP execution.

The following is an example of the first few log lines of an LDA delivery:

dovecot: lda: Debug: Loading modules from directory: /usr/lib/dovecot/modules
dovecot: lda: Debug: Module loaded: /usr/lib/dovecot/modules/lib90_sieve_plugin.so
dovecot: lda(hendrik): Debug: Effective uid=1000, gid=1000, home=/home/hendrik
dovecot: lda(hendrik): Debug: Namespace inbox: type=private, prefix=, sep=, inbox=yes, hidden=no, list=yes, subscriptions=yes location=

The first lines show that LDA has found and loaded the Sieve plugin module. Then it shows for what user it is delivering and where his INBOX is located. LMTP produces similar log lines. If you don't see lines such as the above, your MTA is probably not using Dovecot for local delivery. You can verify whether Dovecot is working correctly by executing dovecot-lda manually.

The Sieve plugin is not Enabled

The Dovecot LDA and LMTP Server services do not provide Sieve support by default.

Sieve support is provided as a separate plugin that needs to be enabled by adding it to mail_plugins in the protocol lda {...} section for the LDA and the protocol lmtp {...} section for LMTP. If this is omitted, Sieve scripts are ignored. See sieve plugin.

Without actually running LDA, you can also check if executing doveconf -f service=lda mail_plugins includes "sieve".

The Sieve plugin is misconfigured or the involved Sieve scripts contain errors

If there is a configuration error or when a Sieve script cannot be compiled and executed, an error is always logged.

Mailbox Names with non-ASCII Characters Cause Problems

This problem most often manifests with the following error message:

error: msgid=<234234.234234@example.com>: failed to store into mailbox 'INBOX/Co&APY-rdineren' (INBOX/Co&-APY-rdineren): Mailbox doesn't exist: INBOX.Co&-APY-rdineren.

The Sieve script causing this error contained the following command:

fileinto "INBOX/Co&APY-rdineren";

The specified mailbox contains the non-ASCII character 'ö'.

Unfortunately, the author of this script used the wrong encoding. This is modified UTF-7 such as used by IMAP. However, Sieve expects UTF-8 for mailbox names. Depending on version and configuration, Dovecot uses modified UTF-7 internally. The Sieve interpreter expects UTF-8 and converts that to UTF-7 when necessary.

When the mailbox is encoded in UTF-7 by the user, the '&' will just be escaped into '&-' during the UTF-7 conversion, yielding an erroneous mailbox name for Dovecot. That is what causes the error message presented above.

Instead, the fileinto command should have looked as follows:

fileinto "INBOX/Coördineren";

The old CMUSieve plugin did use UTF-7 for folder names. Therefore, this problem could have emerged after migrating from CMUSieve to Pigeonhole.