diff --git a/roles/mail_server/molecule/default/molecule.yml b/roles/mail_server/molecule/default/molecule.yml
index 459f5d17b188dd8cf1ba2d69c70a468f75997f90..c7e1b62fe5c69ee43fb388ad3cef74b5f59bbfe6 100644
--- a/roles/mail_server/molecule/default/molecule.yml
+++ b/roles/mail_server/molecule/default/molecule.yml
@@ -19,8 +19,12 @@ lint:
 
 platforms:
 
+
+  # Helpers
+  # =======
+
   - name: clamav-database
-    box: debian/contrib-buster64
+    box: debian/bullseye64
     memory: 512
     cpus: 1
     interfaces:
@@ -32,7 +36,7 @@ platforms:
       synced_folder: true
 
   - name: ldap-server
-    box: debian/contrib-buster64
+    box: debian/bullseye64
     memory: 256
     cpus: 1
     interfaces:
@@ -41,6 +45,10 @@ platforms:
         network_name: private_network
         type: static
 
+
+  # Debian 10 Buster
+  # ================
+
   - name: client1-buster
     groups:
       - client
@@ -71,7 +79,7 @@ platforms:
         network_name: private_network
         type: static
 
-  - name: parameters-mandatory-buster64
+  - name: parameters-mandatory-buster
     groups:
       - parameters-mandatory
       - buster
@@ -84,7 +92,7 @@ platforms:
         network_name: private_network
         type: static
 
-  - name: parameters-optional-buster64
+  - name: parameters-optional-buster
     groups:
       - parameters-optional
       - buster
@@ -97,6 +105,67 @@ platforms:
         network_name: private_network
         type: static
 
+
+  # Debian 11 Bullseye
+  # ================
+
+  - name: client1-bullseye
+    groups:
+      - client
+      - client-relay-allowed
+      - bullseye
+      - smtp-server-requiring-tls
+    box: debian/bullseye64
+    memory: 256
+    cpus: 1
+    interfaces:
+      - auto_config: true
+        ip: 192.168.56.41
+        network_name: private_network
+        type: static
+
+  - name: client2-bullseye
+    groups:
+      - client
+      - client-relay-forbidden
+      - bullseye
+      - smtp-server-refusing-tls
+    box: debian/bullseye64
+    memory: 256
+    cpus: 1
+    interfaces:
+      - auto_config: true
+        ip: 192.168.56.42
+        network_name: private_network
+        type: static
+
+  - name: parameters-mandatory-bullseye
+    groups:
+      - parameters-mandatory
+      - bullseye
+    box: debian/bullseye64
+    memory: 2048
+    cpus: 1
+    interfaces:
+      - auto_config: true
+        ip: 192.168.56.51
+        network_name: private_network
+        type: static
+
+  - name: parameters-optional-bullseye
+    groups:
+      - parameters-optional
+      - bullseye
+    box: debian/bullseye64
+    memory: 2048
+    cpus: 1
+    interfaces:
+      - auto_config: true
+        ip: 192.168.56.52
+        network_name: private_network
+        type: static
+
+
 provisioner:
   name: ansible
   playbooks: