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--- doc:appunti:linux:sa:sieve_filtering_examples [2023/03/22 23:25] – [Pipe a message to an external program] niccolo
+++ doc:appunti:linux:sa:sieve_filtering_examples [2023/03/24 12:54] – [Filtering with Sieve] niccolo
@@ Line 1: / Line 1: @@
 ====== Filtering with Sieve ======
+The **Debian 11 Bullseye** GNU/Linux installs the **Dovecot** mail suite version **2.3.13**, including the **Pigeonhole Sieve** extension **v0.5.13** (via the **dovecot-sieve** package).
+The [[https://doc.dovecot.org/configuration_manual/sieve/pigeonhole_sieve_interpreter/|Pigeonhole Sieve Interpreter]] provides the //pipe//, //filter// and //execute// commands, where the //pipe// was the older one implemented (starting from v0.2). Currently the more modern //execute// command can be used instead of the //pipe// one.
+The following recipes were tested into a **$HOME/.dovecot.sieve** file, i.e. the users's Sieve filter applied by the Dovecot Local Delivery Agent.
 ===== Sender =====
-Storing in different folder upon (envelope) sender:
+Storing messages in different folder upon (envelope) sender:
 <code>
@@ Line 14: / Line 20: @@
 ===== Recipient =====
-Storing in different folder upon destination address:
+Storing messages in different folder upon destination address:
 <code>
@@ Line 25: / Line 31: @@
 ===== Forward and keep a local copy =====
-The **redirect** built-in //action// can be modified by the **:copy** //tag// (which is a built-in extension, but it must enabled using the **require** statement). The '':copy'' means that the message is not completed by the ''redirect'' action; eventually the ''keep'' action will be finally executed.
+The **redirect** built-in //action// can be modified by the **:copy** //tag// (which is a built-in extension, but it must enabled using the **require** statement). The '':copy'' tag means that the message is not completed by the ''redirect'' action; eventually the ''keep'' action will be finally executed.
 <code>
@@ Line 55: / Line 61: @@
 ===== Pipe a message to an external program =====
+To enable the **execute** Sieve command using **Debian 11** you have to edit some configuration files contained into the **/etc/dovecot/conf.d/** directory. Set the **sieve_extension** option editing the file **90-sieve.conf**; in this example both the //filter// and //execute// extensions are loaded:
+<file>
+plugin {
+   ...
+   sieve_extensions = +vnd.dovecot.filter +vnd.dovecot.execute
+   ...
+}
+</file>
+Then you have to edit the **90-sieve-extprograms.conf** configuration file and define the **sieve_execute_socket_dir** and **sieve_execute_bin_dir** options:
+<file>
+plugin {
+  ...
+  sieve_execute_socket_dir = sieve-execute
+  sieve_execute_bin_dir = /usr/local/lib/dovecot/sieve-execute
+  ...
+}
+</file>
+Only the executables contained into //sieve_execute_bin_dir// can be used as //execute// commands in sieve scripts.
+The following example is used to pipe a received message to an external program, which acts as a gateway from the mail system to the SMS mobile network. Only messages originating from some addresses and containing a properly formatted subject are piped to the external program:
 <code>
 require ["vnd.dovecot.execute"];
 # Specially crafted messages are piped to an SMS gateway.
 if allof (
@@ Line 69: / Line 99: @@
 </code>
-The **execute** command is not considered a final action (which "consumes" the message), so the **keep** action is eventually taken.
+Here the **execute** //command// is called with the **:pipe** //tag//, this causes the execution of the external program much like the older ''pipe'' command.
+The **execute** command is not considered a final action (which "consumes" the message), so the **keep** action is eventually taken, saving the message into the INBOX.
   * **[[https://doc.dovecot.org/configuration_manual/sieve/plugins/extprograms/|Pigeonhole Sieve: Extprograms Plugin]]**
   * **[[https://mailutils.org/manual/html_chapter/Sieve-Language.html|GNU Mailutils Sieve]]**