diff --git a/.github/workflows/close_stale_issues.yml b/.github/workflows/close_stale_issues.yml
index 761bf475..c0dcb36f 100644
--- a/.github/workflows/close_stale_issues.yml
+++ b/.github/workflows/close_stale_issues.yml
@@ -6,7 +6,7 @@ on:
 
 jobs:
   stale:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/stale@v3
         with:
diff --git a/.github/workflows/default_on_push.yml b/.github/workflows/default_on_push.yml
index a1ae4a2c..cd7fc031 100644
--- a/.github/workflows/default_on_push.yml
+++ b/.github/workflows/default_on_push.yml
@@ -6,7 +6,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     outputs:
       imagetag: ${{ steps.prep.outputs.imagetag }}
     steps:
@@ -54,7 +54,7 @@ jobs:
 
   test:
     needs: build
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - name: Checkout
         uses: actions/checkout@v2
@@ -68,7 +68,7 @@ jobs:
 
   publish:
     needs: test
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - name: Checkout
         uses: actions/checkout@v2
diff --git a/.github/workflows/linting.yml b/.github/workflows/linting.yml
index f91d662c..275eb053 100644
--- a/.github/workflows/linting.yml
+++ b/.github/workflows/linting.yml
@@ -8,7 +8,7 @@ on:
 
 jobs:
   lint:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - name: Checkout
         uses: actions/checkout@v2
diff --git a/.github/workflows/scheduled_builds.yml b/.github/workflows/scheduled_builds.yml
index e1089a95..9fb5a537 100644
--- a/.github/workflows/scheduled_builds.yml
+++ b/.github/workflows/scheduled_builds.yml
@@ -6,7 +6,7 @@ on:
 
 jobs:
   publish:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - name: Checkout
         uses: actions/checkout@v2
diff --git a/.github/workflows/test_merge_requests.yml b/.github/workflows/test_merge_requests.yml
index d508c5f4..e9ae9dbd 100644
--- a/.github/workflows/test_merge_requests.yml
+++ b/.github/workflows/test_merge_requests.yml
@@ -1,59 +1,40 @@
 name: "Test Merge Requests"
 
-on:
-  pull_request:
-    branches: [ "*" ]
+on: pull_request
 
 jobs:
-  build:
-    runs-on: ubuntu-latest
-    outputs:
-      imagetag: ${{ steps.prep.outputs.imagetag }}
+  build-and-test:
+    runs-on: ubuntu-20.04
     steps:
-      - name: Checkout
+      -
+        name: Checkout
         uses: actions/checkout@v2
         with:
           submodules: recursive
-      - name: Prepare
-        id: prep
-        run: |
-          DOCKER_IMAGE=docker.io/mailserver/testing
-          TAGS="${DOCKER_IMAGE}:${GITHUB_SHA::8},${DOCKER_IMAGE}:latest"
-          echo ::set-output name=tags::${TAGS}
-      - name: Set up QEMU
+      -
+        name: Set up QEMU
         uses: docker/setup-qemu-action@v1
-      - name: Set up Docker Buildx
+      -
+        name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1
         id: buildx
-      - name: Login to DockerHub
-        uses: docker/login-action@v1
-        with:
-          username: ${{ secrets.DOCKER_USERNAME }}
-          password: ${{ secrets.DOCKER_PASSWORD }}
-      - name: Build image locally
+      -
+        name: Build image locally
         uses: docker/build-push-action@v2
         with:
           builder: ${{ steps.buildx.outputs.name }}
-          context: .
-          file: ./Dockerfile
           build-args: |
             VCS_REF=${{ github.sha }}
             VCS_VER=${{ github.ref }}
+          context: .
+          file: ./Dockerfile
+          load: true
           platforms: linux/amd64
-          pull: true
-          push: true
-          tags: ${{ steps.prep.outputs.tags }}
-
-  test:
-    needs: build
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-        with:
-          submodules: recursive
-      - name: run test suite
-        run: |
-          NAME=docker.io/mailserver/testing:${GITHUB_SHA::8} bash -c 'make generate-accounts tests'
+          tags: docker.io/mailserver/testing:ci
+      -
+        name: Run all tests
+        run: >
+          NAME=docker.io/mailserver/testing:ci
+          bash -c 'make generate-accounts tests'
         env:
           CI: true
diff --git a/README.md b/README.md
index 11a40428..54381177 100644
--- a/README.md
+++ b/README.md
@@ -66,10 +66,10 @@ A fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.)
 Download the `docker-compose.yml`, `compose.env`, `mailserver.env` and the `setup.sh` files:
 
 ``` BASH
-wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/stable/setup.sh
-wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/stable/docker-compose.yml
-wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/stable/mailserver.env
-wget -O .env https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/stable/compose.env
+wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master/setup.sh
+wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master/docker-compose.yml
+wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master/mailserver.env
+wget -O .env https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master/compose.env
 
 chmod a+x ./setup.sh
 ```