diff --git a/.well-known/mta-sts.txt b/.well-known/mta-sts.txt
new file mode 100644
index 0000000..abee99e
--- /dev/null
+++ b/.well-known/mta-sts.txt
@@ -0,0 +1,5 @@
+version: STSv1
+mode: testing
+mx: mx01.ionos.co.uk
+mx: mx02.ionos.co.uk
+max_age: 86400