diff --git a/.travis.yml b/.travis.yml
index 21d6cff497c5226e44850b0be62259d55d22f6eb..560c7e638d6454900ff168a6dfb7a10af7432639 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -46,14 +46,14 @@ matrix:
     sudo: required
     dist: trusty
     services: docker
-    env: BEAKER_set="ubuntu-12.04"
+    env: BEAKER_set="ubuntu-14.04"
     bundler_args:
     script: sudo service docker restart ; sleep 10 && bundle exec rspec spec/acceptance/*_spec.rb
   - rvm: default
     sudo: required
     dist: trusty
     services: docker
-    env: BEAKER_set="ubuntu-14.04"
+    env: BEAKER_set="ubuntu-16.04"
     bundler_args:
     script: sudo service docker restart ; sleep 10 && bundle exec rspec spec/acceptance/*_spec.rb
   - rvm: default
diff --git a/metadata.json b/metadata.json
index eadbd7648a91422c6ec30284b42273a9d05dc9ad..44d687fc376b3e4db4743637fda27eecd94ec290 100644
--- a/metadata.json
+++ b/metadata.json
@@ -30,8 +30,8 @@
     {
       "operatingsystem": "Ubuntu",
       "operatingsystemrelease": [
-        "12.04",
-        "14.04"
+        "14.04",
+        "16.04"
       ]
     },
     {
diff --git a/spec/acceptance/postfix_spec.rb b/spec/acceptance/postfix_spec.rb
index ccfbbc6977573ee253c7f2af2845c26e637ed56e..b03b54cd84605a591d8108b32668bac2f474be71 100644
--- a/spec/acceptance/postfix_spec.rb
+++ b/spec/acceptance/postfix_spec.rb
@@ -5,6 +5,22 @@ describe 'postfix class' do
   context 'default parameters' do
     it 'should work idempotently with no errors' do
       pp = <<-EOS
+        # Make sure the default mailer is stopped in docker containers
+        if $::operatingsystem == 'Debian' {
+          service { 'exim4':
+            ensure    => stopped,
+            hasstatus => false,
+            before    => Class['postfix'],
+          }
+        }
+        if $::osfamily == 'RedHat' {
+          service { 'sendmail':
+            ensure    => stopped,
+            hasstatus => false,
+            before    => Class['postfix'],
+          }
+        }
+
         class { 'postfix': }
       EOS