diff --git a/nixos/modules/mail.nix b/nixos/modules/mail.nix
index 71a6559..b8e51f1 100644
--- a/nixos/modules/mail.nix
+++ b/nixos/modules/mail.nix
@@ -98,8 +98,10 @@ in {
             domains = ["fb04184.mathematik.tu-darmstadt.de" "imap.mathebau.de" "smtp.mathebau.de" "mathebau.de"];
             default = true;
           };
+          # HRZ/DFN does spam checking for us and this way we don't need to deal with their possibly broken forwarding setup.
+          spam-filter.enable = false;
+
           # Reevaluate after DKIM and DMARC deployment
-          spam.header.is-spam = "Dummyheader"; # disable moving to spam which would conflict with forwarding
           auth = {
             # TODO check if HRZ and our own VMs conform to these standards and we can validate them strictly
             dkim.verify = "relaxed";
diff --git a/packages/alias-to-sieve/src/lib.rs b/packages/alias-to-sieve/src/lib.rs
index 6622a8a..c0d6842 100644
--- a/packages/alias-to-sieve/src/lib.rs
+++ b/packages/alias-to-sieve/src/lib.rs
@@ -13,28 +13,58 @@ pub struct AliasFile {
 }
 
 #[derive(PartialEq, Eq, Clone, Debug)]
-pub struct OrdEmailAddress(EmailAddress);
+pub struct AliasEmailAddress(EmailAddress);
 
-impl PartialOrd for OrdEmailAddress {
+impl AliasEmailAddress {
+    /// Create an `AliasEmailAddress` from some alias entry.
+    /// Return parameter for complete mail addresses and append the default domain for local parts.
+    pub fn new(
+        alias_entry: &str,
+        default_domain: &FQDN,
+    ) -> Result<AliasEmailAddress, Box<dyn Error>> {
+        let mut addr = alias_entry.trim().to_string();
+        addr = addr.replace(',', "");
+
+        // The domain already fails on instantiation of the FQDN type if it contains an apostrophe.
+        if addr.contains('\'') {
+            return Err(format!(
+                "Mailaddress {addr} contains an apostrophe which breaks the script generation."
+            )
+            .into());
+        }
+
+        if addr.contains('@') {
+            return Ok(AliasEmailAddress(
+                EmailAddress::parse(&addr, None).ok_or::<Box<dyn Error>>(
+                    String::from("Mailaddress {addr} not parsable.").into(),
+                )?,
+            ));
+        }
+        let unsortable_mail = EmailAddress::new(&addr, &default_domain.to_string(), None)?;
+        Ok(AliasEmailAddress(unsortable_mail))
+    }
+}
+
+impl PartialOrd for AliasEmailAddress {
     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
         Some(self.0.to_string().cmp(&other.0.to_string()))
     }
 }
 
-impl Ord for OrdEmailAddress {
+impl Ord for AliasEmailAddress {
     fn cmp(&self, other: &Self) -> Ordering {
         self.0.to_string().cmp(&other.0.to_string())
     }
 }
 
-pub type AliasMap = BTreeMap<OrdEmailAddress, Vec<OrdEmailAddress>>;
+pub type AliasMap = BTreeMap<AliasEmailAddress, Vec<AliasEmailAddress>>;
 
 /// Read a virtual alias file <https://www.postfix.org/virtual.5.html>
 /// and convert it to a map of destination addresses to a list of their final forwarding addresses.
 pub fn parse_alias_to_map(alias_files: Vec<AliasFile>) -> Result<AliasMap, Box<dyn Error>> {
     // File must exist in the current path
     let mut redirect_map: AliasMap = AliasMap::new();
-    let mut destinations: Vec<OrdEmailAddress> = Vec::new();
+    let mut destinations: Vec<AliasEmailAddress> = Vec::new();
 
     // Extract all pairs (destination to redirect addresses) from the alias files
     for alias_file in alias_files {
@@ -48,25 +78,23 @@ pub fn parse_alias_to_map(alias_files: Vec<AliasFile>) -> Result<AliasMap, Box<d
                 continue;
             }
 
-            if destination.contains('\'') {
-                return Err(format!("Mailaddress {destination} contains an apostrophe which is not allowed by HRZ.")
-                .into());
-            }
-
-            let redirects: Vec<OrdEmailAddress> = line
+            let redirects: Vec<AliasEmailAddress> = line
                 .split_at(line.find(char::is_whitespace).unwrap_or(0))
                 .1
                 .split(' ')
                 .filter(|address| !address.trim().to_string().replace(',', "").is_empty())
-                .map(|addr| to_mailaddress(addr, &alias_file.default_domain))
+                .map(|addr| AliasEmailAddress::new(addr, &alias_file.default_domain))
                 .collect::<Result<Vec<_>, _>>()?;
 
             if redirects.is_empty() {
                 continue;
             }
-            destinations.push(to_mailaddress(destination, &alias_file.default_domain)?);
+            destinations.push(AliasEmailAddress::new(
+                destination,
+                &alias_file.default_domain,
+            )?);
             redirect_map.insert(
-                to_mailaddress(destination, &alias_file.default_domain)?,
+                AliasEmailAddress::new(destination, &alias_file.default_domain)?,
                 redirects,
             );
         }
@@ -105,24 +133,6 @@ pub fn parse_alias_to_map(alias_files: Vec<AliasFile>) -> Result<AliasMap, Box<d
     Ok(redirect_map)
 }
 
-/// Create an `OrdEmailAddress` from some alias entry.
-/// Return parameter for complete mail addresses and append the default domain for local parts.
-fn to_mailaddress(
-    alias_entry: &str,
-    default_domain: &FQDN,
-) -> Result<OrdEmailAddress, Box<dyn Error>> {
-    let mut addr = alias_entry.trim().to_string();
-    addr = addr.replace(',', "");
-    if addr.contains('@') {
-        return Ok(OrdEmailAddress(
-            EmailAddress::parse(&addr, None)
-                .ok_or::<Box<dyn Error>>(String::from("Mailaddress {addr} not parsable.").into())?,
-        ));
-    }
-    let unsortable_mail = EmailAddress::new(&addr, &default_domain.to_string(), None)?;
-    Ok(OrdEmailAddress(unsortable_mail))
-}
-
 // The output is wrapped in a Result to allow matching on errors.
 // Returns an Iterator to the Reader of the lines of the file.
 pub fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
@@ -196,9 +206,17 @@ mod tests {
     }
 
     #[test]
-    fn apostrophe_detection() {
+    fn apostrophe_destination_detection() {
         let result = parse_alias_to_map(vec![AliasFile {
-            content: read_lines("testdata/apostrophe.aliases").unwrap(),
+            content: read_lines("testdata/apostrophe_destination.aliases").unwrap(),
+            default_domain: FQDN::from_str("example.com").unwrap(),
+        }]);
+        assert!(result.is_err());
+    }
+    #[test]
+    fn apostrophe_redirect_detection() {
+        let result = parse_alias_to_map(vec![AliasFile {
+            content: read_lines("testdata/apostrophe_redirect.aliases").unwrap(),
             default_domain: FQDN::from_str("example.com").unwrap(),
         }]);
         assert!(result.is_err());
diff --git a/packages/alias-to-sieve/testdata/apostrophe.aliases b/packages/alias-to-sieve/testdata/apostrophe.aliases
deleted file mode 100644
index 37a6f91..0000000
--- a/packages/alias-to-sieve/testdata/apostrophe.aliases
+++ /dev/null
@@ -1,2 +0,0 @@
-# Apostrophes are not allowed by HRZ
-'orga me@example.com
diff --git a/packages/alias-to-sieve/testdata/apostrophe_destination.aliases b/packages/alias-to-sieve/testdata/apostrophe_destination.aliases
new file mode 100644
index 0000000..5cc3e26
--- /dev/null
+++ b/packages/alias-to-sieve/testdata/apostrophe_destination.aliases
@@ -0,0 +1,2 @@
+# Apostrophes are not allowed
+'orga me@example.com
diff --git a/packages/alias-to-sieve/testdata/apostrophe_redirect.aliases b/packages/alias-to-sieve/testdata/apostrophe_redirect.aliases
new file mode 100644
index 0000000..d6b499f
--- /dev/null
+++ b/packages/alias-to-sieve/testdata/apostrophe_redirect.aliases
@@ -0,0 +1,2 @@
+# Apostrophes are not allowed
+orga me@e'xample.com