diff --git a/admin_manual/installation/nginx-root.conf.sample b/admin_manual/installation/nginx-root.conf.sample
index 99a6da5c1ce..56fd25acf09 100644
--- a/admin_manual/installation/nginx-root.conf.sample
+++ b/admin_manual/installation/nginx-root.conf.sample
@@ -143,6 +143,10 @@ server {
         fastcgi_request_buffering off;
 
         fastcgi_max_temp_file_size 0;
+
+        # Horde, used by nextcloud mail app, needs $_SERVER['SERVER_NAME'] to generate Message-ID header
+        # See also: https://github.com/nextcloud/mail/issues/5764
+        fastcgi_param SERVER_NAME $host;
     }
 
     location ~ \.(?:css|js|svg|gif|png|jpg|ico|wasm|tflite|map)$ {