diff --git a/backend/src/main/resources/application-prod.yml b/backend/src/main/resources/application-prod.yml
index 6d5c219..e86dfae 100644
--- a/backend/src/main/resources/application-prod.yml
+++ b/backend/src/main/resources/application-prod.yml
@@ -4,6 +4,13 @@ spring:
     # Prod DBs created before seeds moved to db/dev-migration still list V2/V4/V6 in history.
     ignore-migration-patterns: '*:missing'
 
+  # docker profile disables STARTTLS for Mailpit; prod must re-enable for Resend SMTP.
+  mail:
+    properties:
+      mail.smtp.auth: true
+      mail.smtp.starttls.enable: true
+      mail.smtp.starttls.required: true
+
 app:
   admin:
     email: ${ADMIN_EMAIL}