diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index c495b3ec..55595838 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -295,6 +295,21 @@ jobs:
         shell: bash
         run: |
           echo "BRANCH=${GITHUB_REF#refs/heads/}" >> $GITHUB_ENV
+        #For branch TESTING, we set the image tag to PR-xxxx
+      - name: Derive MAILU_VERSION for branch testing
+        if: ${{ env.BRANCH == 'testing' }}
+        shell: bash
+        env:
+          COMMIT_MESSAGE: ${{ github.event.head_commit.message }}
+        run: |
+          echo "MAILU_VERSION=pr-${COMMIT_MESSAGE//[!0-9]/}" >> $GITHUB_ENV
+      - name: Derive MAILU_VERSION for other branches than testing
+        if: ${{ env.BRANCH != 'testing' }}
+        shell: bash
+        env:
+          MAILU_BRANCH: ${{ env.BRANCH }}
+        run: |
+          echo "MAILU_VERSION=${{ env.MAILU_BRANCH }}" >> $GITHUB_ENV
       - name: Create folder for storing images
         run: |
           sudo mkdir -p /images