From 3e8f920ac3b6708c62e4ee8e8ef75df14bafa3c3 Mon Sep 17 00:00:00 2001
From: Michael Schlapa <michael.schlapa@uni-duesseldorf.de>
Date: Mon, 7 Oct 2024 17:09:42 +0200
Subject: [PATCH] Added sieve rule to change mail subject

---
 mailserver/sieve.md | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/mailserver/sieve.md b/mailserver/sieve.md
index 3753286..d6a6805 100644
--- a/mailserver/sieve.md
+++ b/mailserver/sieve.md
@@ -1,6 +1,6 @@
 # Sieve
 
-### Sieve rule to automatically sort mails by alias
+### Rule to automatically sort mails by alias
 
 This Sieve rule filters mails by the mail alias they were sent to.
 Specifically, it uses a custom suffix separated by a dot: `.([0-9a-zA-Z]*)`
@@ -17,3 +17,23 @@ if allof (header :regex "to" "^<name>.([0-9a-zA-Z]*)@<domain.tld>$")
         stop;
 }
 ```
+
+### Rule to change Subject of a mail on server
+
+My alma mater introduced a change that subjects of all "external" mails are prefixed with `[Extern]`.
+I don't like that so I wrote a Sieve rule to remove it. The rule relies on some functions which need to be `required`.
+
+```
+require ["fileinto", "editheader", "variables", "regex"];
+
+if allof (header :contains "subject" "[Extern]")
+{
+    # Match the subject w/o "[Extern]"
+    if header :regex "Subject" "^\\[Extern\\] (.*)$" {
+        # Delete header
+        deleteheader "Subject";
+        # Add stripped header again
+        addheader :last "Subject" "${1}";
+    }
+}
+```