diff --git a/_examples/dkim-proxy/README.md b/_examples/dkim-proxy/README.md
new file mode 100644
index 0000000..7009df4
--- /dev/null
+++ b/_examples/dkim-proxy/README.md
@@ -0,0 +1,5 @@
+# smtpd dkim-proxy
+
+## Important Note
+
+The dependency `github.com/eaigner/dkim` is no longer available thus the example can not be built.
diff --git a/_examples/dkim-proxy/go.mod b/_examples/dkim-proxy/go.mod
new file mode 100644
index 0000000..65a2132
--- /dev/null
+++ b/_examples/dkim-proxy/go.mod
@@ -0,0 +1,5 @@
+module github.com/chrj/smtpd/_examples/dkim-proxy
+
+go 1.14
+
+require github.com/eaigner/dkim v0.0.0-20150301120808-6fe4a7ee9cfb
diff --git a/go.sum b/_examples/dkim-proxy/go.sum
similarity index 100%
rename from go.sum
rename to _examples/dkim-proxy/go.sum
diff --git a/examples/dkim-proxy/main.go b/_examples/dkim-proxy/main.go
similarity index 100%
rename from examples/dkim-proxy/main.go
rename to _examples/dkim-proxy/main.go
diff --git a/go.mod b/go.mod
index f5c2391..a883ba1 100644
--- a/go.mod
+++ b/go.mod
@@ -1,5 +1,3 @@
 module github.com/chrj/smtpd
 
 go 1.14
-
-require github.com/eaigner/dkim v0.0.0-20150301120808-6fe4a7ee9cfb