diff --git a/setup/mail-postfix.sh b/setup/mail-postfix.sh
index f117267f..4cfcbaa1 100755
--- a/setup/mail-postfix.sh
+++ b/setup/mail-postfix.sh
@@ -226,7 +226,7 @@ cat > /var/lib/mailinabox/mta-sts.txt << EOF
 version: STSv1
 mode: enforce
 mx: $PRIMARY_HOSTNAME
-max_age: 86400
+max_age: 10368000
 EOF
 chmod a+r /var/lib/mailinabox/mta-sts.txt