diff --git a/README.rst b/README.rst
index 5fa04ed..0a5577e 100644
--- a/README.rst
+++ b/README.rst
@@ -9,12 +9,11 @@ An installer which deploy a complete mail server based on Modoboa.
 
    This tool is still in beta stage, it has been tested on:
 
-   * Debian Buster (10) / Bullseye (11)
+   * Debian 10 and upper
    * Ubuntu Bionic Beaver (18.04) and upper
-   * CentOS 7
 
 .. warning::
-      
+
    ``/tmp`` partition must be mounted without the ``noexec`` option.
 
 .. note::
@@ -92,8 +91,8 @@ You can activate it as follows::
 
 It will automatically install latest versions of modoboa and its plugins.
 
-Backup mode 
-------------
+Backup mode
+-----------
 
 An experimental backup mode is available.
 
diff --git a/modoboa_installer/compatibility_matrix.py b/modoboa_installer/compatibility_matrix.py
index f610124..f1db5f9 100644
--- a/modoboa_installer/compatibility_matrix.py
+++ b/modoboa_installer/compatibility_matrix.py
@@ -21,13 +21,14 @@ COMPATIBILITY_MATRIX = {
         "modoboa-sievefilters": ">=1.1.1",
         "modoboa-webmail": ">=1.2.0",
     },
-    "2.1.0": {
-        "modoboa-pdfcredentials": None,
-        "modoboa-dmarc": None,
-        "modoboa-imap-migration": None,
-    },
 }
 
 EXTENSIONS_AVAILABILITY = {
     "modoboa-contacts": "1.7.4",
 }
+
+REMOVED_EXTENSIONS = {
+    "modoboa-pdfcredentials": "2.1.0",
+    "modoboa-dmarc": "2.1.0",
+    "modoboa-imap-migration": "2.1.0"
+}
diff --git a/modoboa_installer/scripts/modoboa.py b/modoboa_installer/scripts/modoboa.py
index 9c18475..3778bec 100644
--- a/modoboa_installer/scripts/modoboa.py
+++ b/modoboa_installer/scripts/modoboa.py
@@ -65,12 +65,16 @@ class Modoboa(base.Installer):
 
     def is_extension_ok_for_version(self, extension, version):
         """Check if extension can be installed with this modo version."""
-        if extension not in compatibility_matrix.EXTENSIONS_AVAILABILITY:
-            return True
         version = utils.convert_version_to_int(version)
-        min_version = compatibility_matrix.EXTENSIONS_AVAILABILITY[extension]
-        min_version = utils.convert_version_to_int(min_version)
-        return version >= min_version
+        if extension in compatibility_matrix.EXTENSIONS_AVAILABILITY:
+            min_version = compatibility_matrix.EXTENSIONS_AVAILABILITY[extension]
+            min_version = utils.convert_version_to_int(min_version)
+            return version >= min_version
+        if extension in compatibility_matrix.REMOVED_EXTENSIONS:
+            max_version = compatibility_matrix.REMOVED_EXTENSIONS[extension]
+            max_version = utils.convert_version_to_int(max_version)
+            return version < max_version
+        return True
 
     def _setup_venv(self):
         """Prepare a dedicated virtualenv."""
@@ -80,6 +84,13 @@ class Modoboa(base.Installer):
         version = self.config.get("modoboa", "version")
         if version == "latest":
             packages += ["modoboa"] + self.extensions
+            for extension in list(self.extensions):
+                if extension in compatibility_matrix.REMOVED_EXTENSIONS.keys():
+                    self.extensions.remove(extension)
+            self.extensions = [
+                extension for extension in self.extensions
+                if extension not in compatibility_matrix.REMOVED_EXTENSIONS
+            ]
         else:
             matrix = compatibility_matrix.COMPATIBILITY_MATRIX[version]
             packages.append("modoboa=={}".format(version))
diff --git a/run.py b/run.py
index 9ab6841..bdc7b5a 100755
--- a/run.py
+++ b/run.py
@@ -38,6 +38,12 @@ PRIMARY_APPS = [
 def installation_disclaimer(args, config):
     """Display installation disclaimer."""
     hostname = config.get("general", "hostname")
+    utils.printcolor(
+        "Notice:\n"
+        "It is recommanded to run this installer on a FRESHLY installed server.\n"
+        "(ie. with nothing special already installed on it)\n",
+        utils.CYAN
+    )
     utils.printcolor(
         "Warning:\n"
         "Before you start the installation, please make sure the following "
@@ -48,7 +54,7 @@ def installation_disclaimer(args, config):
             hostname.replace(".{}".format(args.domain), ""),
             hostname
         ),
-        utils.CYAN
+        utils.YELLOW
     )
     utils.printcolor(
         "Your mail server will be installed with the following components:",