set expire headers only for mailu content

also moved robots.txt from config to static folder.

core/nginx/conf/nginx.conf

@@ -57,11 +57,6 @@ http {
           proxy_pass http://127.0.0.1:8008;
       }
       {% endif %}
-      # robots.txt
-      location = /robots.txt {
-        add_header Content-Type text/plain;
-        return 200 "User-agent: *\nDisallow: /\n";
-      }
       # redirect to https
       location / {
         return 301 https://$host$request_uri;
@@ -111,8 +106,6 @@ http {
       # Remove headers to prevent duplication and information disclosure
       proxy_hide_header X-XSS-Protection;
       proxy_hide_header X-Powered-By;
-      
-      expires $expires;
 
       add_header X-Frame-Options 'SAMEORIGIN';
       add_header X-Content-Type-Options 'nosniff';
@@ -132,18 +125,12 @@ http {
         return 403;
       }
       {% else %}
-
-      # robots.txt
-      location = /robots.txt {
-        add_header Content-Type text/plain;
-        return 200 "User-agent: *\nDisallow: /\n";
-      }
-
       include /overrides/*.conf;
 
       # Actual logic
       {% if WEB_WEBMAIL != '/' and WEBROOT_REDIRECT != 'none' %}
       location / {
+        expires $expires;
       {% if WEBROOT_REDIRECT %}
         try_files $uri {{ WEBROOT_REDIRECT }};
       {% else %}
@@ -198,6 +185,7 @@ http {
         include /etc/nginx/proxy.conf;
         proxy_set_header X-Forwarded-Prefix {{ WEB_ADMIN }};
         proxy_pass http://$admin;
+        expires $expires;
       }
 
       location {{ WEB_ADMIN }}/antispam {

core/nginx/static/robots.txt

@@ -0,0 +1,2 @@
+User-agent: *
+Disallow: /