diff --git a/nixos/machines/lobon/backupKey.yaml b/nixos/machines/lobon/backupKey.yaml
new file mode 100644
index 0000000..3095894
--- /dev/null
+++ b/nixos/machines/lobon/backupKey.yaml
@@ -0,0 +1,39 @@
+backupKey: ENC[AES256_GCM,data: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,iv:ghvgkC6qFO/0tvsc7igCoZy7am8eNsd21WYCSAKiZDs=,tag:MFnk/Nnw+cloN+x7sd4LLg==,type:str]
+sops:
+    kms: []
+    gcp_kms: []
+    azure_kv: []
+    hc_vault: []
+    age:
+        - recipient: age1rasjnr2tlv9y70sj0z0hwpgpxdc974wzg5umtx2pnc6z0p05u3js6r8sln
+          enc: |
+            -----BEGIN AGE ENCRYPTED FILE-----
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBaNVExTHQrY2h1M3RZOEdU
+            Wm5kdDBHZ1NmZGpQU0VOYWtjOTdBVURQZkJnCmZzWTEvSWxvMFk4NlFOVnBDbm9q
+            Tncva0VyMGVDL29ZZ0YxeGE3RFBUS3cKLS0tIDluK05NMUNNM3pEUmlCNE9BV3lT
+            L0dPYTBwbjJzUmJnYktiM2JBME5LM3cKvPwth4DxQgFYhvr9vJLfeaiNc+UfAo4c
+            RdXPLkwtq3vksrU1IR54tHcUJ0yZiZ1HxxGp3PCPaXXJiUykllnJPw==
+            -----END AGE ENCRYPTED FILE-----
+        - recipient: age1epz92k2rkp43hkrg3u0jgkzhnkwx8y43kag7rvfzwl9wcddelvusyetxl7
+          enc: |
+            -----BEGIN AGE ENCRYPTED FILE-----
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBRdFV0OVA5VTBuOVhsL3lp
+            MFpDN2RHVDExck5vcWpDNDNPM2k3S1FqQUFFCjNreXdSbDFXOHJ4b21mNGlZb0xQ
+            YUh0WVNGN2o1aFVaaGpxbmk4aUQ4ZTAKLS0tIHhtci84Zk1zZlBOOHk4a3VKUlM1
+            MXNZbWdpVEJiTTlIRERLYzBlNWxBMlUK4Z8JLlN5FOegfdg5njhHjbCwAm/f+kJS
+            buOHGWzWirW0ZibOP+fikzJwdIzIsX8v8tGaV89nQwf0hrxK0748Hg==
+            -----END AGE ENCRYPTED FILE-----
+        - recipient: age12nz7dtc0m5wasxm4r9crtkgwnzvauyfp0xh0n8z8jld0arn9ea9qe0agvn
+          enc: |
+            -----BEGIN AGE ENCRYPTED FILE-----
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBZa2pUZlZsVmhPU242d0Nj
+            bi9BSlJBU1Q1cFU4ZjA4NnlJNmdwaVFBc2xNCjJlSG5UaDFnSzFHZ01RVVNjOHY5
+            L1JVUit6SThvbGRIU0loNmtZanllNXcKLS0tIFhMR1pxRmlGQWFEQURiRFJoMWJZ
+            dlExV2xTVWR6bWI3VCtSdU81SmtqYncKLFQczlIj89vzlfgE33w6ktotYFdxaWr9
+            YyewbY8qZmOUGQ4xKlZmhojeMh/FEH8dGNEf1AxnKbuQdnW6lqGR/w==
+            -----END AGE ENCRYPTED FILE-----
+    lastmodified: "2024-03-31T16:01:00Z"
+    mac: ENC[AES256_GCM,data:AawTzIXyX+3FyFpw8pXFeVJJtXN7ZpTFnUqhedC2vcbbNUzMMt1X0SaxtNNJ5chZI/tYHn59FT6zznl1eO4Xn29Zc2Up4dkT1BE4yqkEG0hiCFXrXMz/PaHfROzBhIWCVyF4fYj6MZKg1iBBxhWRqhJlQ1q4UVkoaITRUKpFJgs=,iv:3lTPOQ8VjmP3WNGbFK2yLU4Ks1KviNS/l7TH4SnvSUs=,tag:KUbAU6+76/Uxj2Wn9EnqnA==,type:str]
+    pgp: []
+    unencrypted_suffix: _unencrypted
+    version: 3.8.1
diff --git a/nixos/machines/lobon/configuration.nix b/nixos/machines/lobon/configuration.nix
index 553bfe4..506d637 100644
--- a/nixos/machines/lobon/configuration.nix
+++ b/nixos/machines/lobon/configuration.nix
@@ -18,4 +18,19 @@
   networking.hostName = "lobon";
   vmNetwork.ipv4 = "192.168.0.22";
   system.stateVersion = "23.11";
+
+  sops.secrets = {
+    allowlistPass = {
+      sopsFile = ./allowlistPass.yaml;
+      owner = "mailman";
+      group = "mailman";
+      mode = "0400";
+    };
+    backupKey = {
+      sopsFile = ./backupKey.yaml;
+      owner = "root";
+      group = "root";
+      mode = "0400";
+    };
+  };
 }
diff --git a/nixos/modules/borgbackup.nix b/nixos/modules/borgbackup.nix
index b5cbe40..f88df4b 100644
--- a/nixos/modules/borgbackup.nix
+++ b/nixos/modules/borgbackup.nix
@@ -83,6 +83,13 @@ in {
           path = "/var/lib/backups/ithaqua";
           allowSubRepos = true;
         };
+        lobon = {
+          authorizedKeysAppendOnly = [
+            "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICEptjf1UWRlo6DG9alAIRwkSDUAVHwDKkHC6/DeYKzi Lobon Backup"
+          ];
+          path = "/var/lib/backups/lobon";
+          allowSubRepos = true;
+        };
         sanctamariamaterdei = {
           authorizedKeysAppendOnly = [
             "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIH9Le5OI4ympQ0mQKYHmxgxGF598rzpD5VVpWK1mGfd8 Sanctamariamaterdei Backupsystem"
diff --git a/nixos/modules/mailman.nix b/nixos/modules/mailman.nix
index 7d233fd..8156d32 100644
--- a/nixos/modules/mailman.nix
+++ b/nixos/modules/mailman.nix
@@ -37,7 +37,7 @@ in {
           proxy_interfaces = "130.83.2.184";
           smtputf8_enable = "no"; # HRZ does not know SMTPUTF8
         };
-        relayHost = "mailout.hrz.tu-darmstadt.de"; # Relay to HRZ (see https://www.hrz.tu-darmstadt.de/services/it_services/email_infrastruktur/index.de.jsp)
+        relayHost = "192.168.0.24"; # Relay to eihort which relays to HRZ (see https://www.hrz.tu-darmstadt.de/services/it_services/email_infrastruktur/index.de.jsp)
       };
       mailman = {
         enable = true;
@@ -60,6 +60,7 @@ in {
         "/var/lib/mailman"
         "/var/lib/mailman-web"
       ];
+      files = ["/root/.ssh/known_hosts"]; # for the backup server bragi
     };
 
     security.acme.defaults.email = cfg.siteOwner;
@@ -95,11 +96,25 @@ in {
         PrivateTmp = true;
       };
     };
-    sops.secrets.allowlistPass = {
-      sopsFile = ../machines/lobon/allowlistPass.yaml;
-      owner = "mailman";
-      group = "mailman";
-      mode = "0400";
+
+    # Backups
+    services.borgbackup.jobs.mailman = {
+      paths = [
+        "/var/lib/mailman/data"
+        "/var/lib/mailman-web"
+      ];
+      encryption.mode = "none"; # Otherwise the key is next to the backup or we have human interaction.
+      environment = {
+        BORG_RSH = "ssh -i /run/secrets/backupKey";
+        # “Borg ensures that backups are not created on random drives that ‘just happen’ to contain a Borg repository.”
+        # https://borgbackup.readthedocs.io/en/stable/deployment/automated-local.html
+        # We don't want this in order to not need to persist borg cache and simplify new deployments.
+        BORG_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK = "yes";
+      };
+      repo = "borg@192.168.1.11:lobon"; # TODO for https://gitea.mathebau.de/Fachschaft/nixConfig/issues/33
+      startAt = "daily";
+      user = "root";
+      group = "root";
     };
   };
 }