diff --git a/changelogs/unreleased/sh-fix-issue-63910.yml b/changelogs/unreleased/sh-fix-issue-63910.yml
new file mode 100644
index 00000000000..50312558c57
--- /dev/null
+++ b/changelogs/unreleased/sh-fix-issue-63910.yml
@@ -0,0 +1,5 @@
+---
+title: Fix attachments using the wrong URLs in e-mails
+merge_request: 30197
+author:
+type: fixed
diff --git a/lib/banzai/filter/relative_link_filter.rb b/lib/banzai/filter/relative_link_filter.rb
index 80c84c0f622..88836e12e61 100644
--- a/lib/banzai/filter/relative_link_filter.rb
+++ b/lib/banzai/filter/relative_link_filter.rb
@@ -56,10 +56,10 @@ module Banzai
       def process_link_to_upload_attr(html_attr)
         path_parts = [Addressable::URI.unescape(html_attr.value)]
 
-        if group
-          path_parts.unshift(relative_url_root, 'groups', group.full_path, '-')
-        elsif project
+        if project
           path_parts.unshift(relative_url_root, project.full_path)
+        elsif group
+          path_parts.unshift(relative_url_root, 'groups', group.full_path, '-')
         else
           path_parts.unshift(relative_url_root)
         end
diff --git a/spec/helpers/markup_helper_spec.rb b/spec/helpers/markup_helper_spec.rb
index 597c8f836a9..6c6410cee9b 100644
--- a/spec/helpers/markup_helper_spec.rb
+++ b/spec/helpers/markup_helper_spec.rb
@@ -50,6 +50,43 @@ describe MarkupHelper do
         expect(markdown(actual, project: second_project)).to match(expected)
       end
     end
+
+    describe 'uploads' do
+      let(:text) { "![ImageTest](/uploads/test.png)" }
+      let(:group) { create(:group) }
+
+      subject { helper.markdown(text) }
+
+      describe 'inside a project' do
+        it 'renders uploads relative to project' do
+          expect(subject).to include("#{project.full_path}/uploads/test.png")
+        end
+      end
+
+      describe 'inside a group' do
+        before do
+          helper.instance_variable_set(:@group, group)
+          helper.instance_variable_set(:@project, nil)
+        end
+
+        it 'renders uploads relative to the group' do
+          expect(subject).to include("#{group.full_path}/-/uploads/test.png")
+        end
+      end
+
+      describe "with a group in the context" do
+        let(:project_in_group) { create(:project, group: group) }
+
+        before do
+          helper.instance_variable_set(:@group, group)
+          helper.instance_variable_set(:@project, project_in_group)
+        end
+
+        it 'renders uploads relative to project' do
+          expect(subject).to include("#{project_in_group.path_with_namespace}/uploads/test.png")
+        end
+      end
+    end
   end
 
   describe '#markdown_field' do