diff --git a/rootfs/etc/cont-init.d/02-dhparam b/rootfs/etc/cont-init.d/02-dhparam
new file mode 100644
index 0000000..7bb26b0
--- /dev/null
+++ b/rootfs/etc/cont-init.d/02-dhparam
@@ -0,0 +1,5 @@
+#!/usr/bin/with-contenv sh
+
+if [ ! -f /etc/ssl/mail/dh.pem ]; then
+    openssl dhparam -out /etc/ssl/mail/dh.pem ${SSL_DH_LENGTH:-2048}
+fi