Do not deny HTTP access upon TLS error when the flavor is mail

core/nginx/conf/nginx.conf

@@ -62,7 +62,7 @@ http {
       {% endif %}
 
       # If TLS is failing, prevent access to anything except certbot
-      {% if TLS_ERROR %}
+      {% if TLS_ERROR and not TLS_FLAVOR == "mail" %}
       location / {
         return 403;
       }