Enable SMTPUTF8. We talk to our own VM that supports it.

nixos/modules/mail.nix

@@ -194,6 +194,8 @@ in {
           # because only TOML-based keys may use macros to load files from disk.
           # We want this to be able to load our sieve-script for mail forwarding.
           # See https://stalw.art/docs/configuration/overview/#local-and-database-settings for more details.
+          #
+          # Unfortunately, the set of served domains as well as the catch-all accounts are still not configured via this nix module.
           config.local-keys =
             [
               "store.*"
@@ -237,7 +239,7 @@ in {
                 private-key = "%{file:/run/secrets/dkim_rsa}%";
                 domain = "${domain}";
                 selector = "rsa-default";
-                headers = ["From" "To" "Cc" "Date" "Subject" "Message-ID" "Organization" "MIME-Version" "Content-Type" "In-Reply-To" "References" "List-Id" "User-Agent" "Thread-Topic" "Thread-Index"];
+                headers = ["From" "To" "Cc" "Date" "Subject" "Message-ID" "Organization" "MIME-Version" "Content-Type" "In-Reply-To" "References" "List-Id" "User-Agent" "Thread-Topic" "Thread-Index"]; # default from https://stalw.art/docs/smtp/authentication/dkim/sign#signatures
                 algorithm = "rsa-sha256";
                 canonicalization = "relaxed/relaxed";
               };

nixos/modules/mailman.nix

@@ -32,7 +32,6 @@ in {
         config = {
           transport_maps = ["hash:/var/lib/mailman/data/postfix_lmtp"];
           local_recipient_maps = ["hash:/var/lib/mailman/data/postfix_lmtp"];
-          smtputf8_enable = "no"; # HRZ does not know SMTPUTF8
         };
         relayHost = "mathebau.de"; # Relay to mail vm which relays to HRZ (see https://www.hrz.tu-darmstadt.de/services/it_services/email_infrastruktur/index.de.jsp)
       };