Return 500 if email delivery fails.

src/routes/subscriptions.rs

@@ -59,13 +59,14 @@ pub async fn subscribe(
         .commit()
         .await
         .map_err(|_| HttpResponse::InternalServerError().finish())?;
-    let _ = send_confirmation_email(
+    send_confirmation_email(
         &email_client,
         new_subscriber,
         &base_url.0,
         &subscription_token,
     )
-    .await;
+    .await
+    .map_err(|_| HttpResponse::InternalServerError().finish())?;
     Ok(HttpResponse::Ok().finish())
 }
 

tests/api/subscriptions.rs

@@ -8,6 +8,12 @@ async fn subscribe_returns_a_200_for_valid_form_data() {
     let app = spawn_app().await;
     let body = "name=le%20guin&email=ursula_le_guin%40gmail.com";
 
+    Mock::given(path("/email"))
+        .and(method("POST"))
+        .respond_with(ResponseTemplate::new(200))
+        .mount(&app.email_server)
+        .await;
+
     // Act
     let response = app.post_subscriptions(body.into()).await;