diff --git a/server/src/lib.rs b/server/src/lib.rs
index c184c91..9e84d05 100644
--- a/server/src/lib.rs
+++ b/server/src/lib.rs
@@ -121,11 +121,11 @@ impl Transformer for InlineStyle {
 struct AddOutlink(Option<url::Url>);
 
 impl Transformer for AddOutlink {
-    fn should_run(&self, _: &str) -> bool {
-        self.0
-            .as_ref()
-            .map(|l| l.scheme().starts_with("http"))
-            .unwrap_or(false)
+    fn should_run(&self, html: &str) -> bool {
+        if let Some(link) = &self.0 {
+            return link.scheme().starts_with("http") && !html.contains(link.as_str());
+        }
+        false
     }
     fn transform(&self, html: &str) -> Result<String, TransformError> {
         if let Some(url) = &self.0 {