diff --git a/bundles/letsencrypt/metadata.py b/bundles/letsencrypt/metadata.py
index a7e8f74..24f9d9e 100644
--- a/bundles/letsencrypt/metadata.py
+++ b/bundles/letsencrypt/metadata.py
@@ -7,7 +7,9 @@ defaults = {
         },
     },
     'letsencrypt': {
-        'domains': {},
+        'domains': {
+            # 'example.com': {'alias1.example.com', 'alias2.example.com'},
+        },
     },
     'pacman': {
         'packages': {
@@ -52,7 +54,7 @@ def delegated_domains(metadata):
     return {
         'letsencrypt': {
             'domains': {
-                domain: {}
+                domain: set()
                     for other_node in repo.nodes
                     if other_node.has_bundle('letsencrypt')
                         and other_node.metadata.get('letsencrypt/delegate_to_node', None) == node.name
diff --git a/bundles/nginx/metadata.py b/bundles/nginx/metadata.py
index 2444ec9..99aa6f9 100644
--- a/bundles/nginx/metadata.py
+++ b/bundles/nginx/metadata.py
@@ -104,7 +104,7 @@ def letsencrypt(metadata):
     return {
         'letsencrypt': {
             'domains': {
-                domain: {} for domain in metadata.get('nginx/vhosts')
+                domain: set() for domain in metadata.get('nginx/vhosts')
             },
             'reload_after': {
                 'nginx',
diff --git a/nodes/htz.mails.py b/nodes/htz.mails.py
index dca934a..b190787 100644
--- a/nodes/htz.mails.py
+++ b/nodes/htz.mails.py
@@ -32,17 +32,17 @@
         'bind': {
             'hostname': 'resolver.name',
             'zones': {
-                'sublimity.de': [],
-                'freibrief.net': [],
-                'nadenau.net': [],
-                'naeder.net': [],
-                'rolfwerner.eu': [],
-                'wettengl.net': [],
-                'wingl.de': [],
-                'woodpipe.de': [],
-                'ckn.li': [],
-                'islamicstate.eu': [],
-                'hausamsilberberg.de': [],
+                'sublimity.de': {},
+                'freibrief.net': {},
+                'nadenau.net': {},
+                'naeder.net': {},
+                'rolfwerner.eu': {},
+                'wettengl.net': {},
+                'wingl.de': {},
+                'woodpipe.de': {},
+                'ckn.li': {},
+                'islamicstate.eu': {},
+                'hausamsilberberg.de': {},
             },
         },
         'dns': {
@@ -61,9 +61,9 @@
         },
         'letsencrypt': {
             'domains': {
-                'ckn.li': {},
-                'sublimity.de': {},
-                'freibrief.net': {},
+                'ckn.li': set(),
+                'sublimity.de': set(),
+                'freibrief.net': set(),
             },
         },
         'mailserver': {