Update s3_file_storage.rst

docs/howto/s3_file_storage.rst

@@ -23,6 +23,12 @@ Or set environment variables `S3_ACCESS_KEY` and `S3_SECRET_KEY` instead of usin
     export S3_ACCESS_KEY=<login> 
     export S3_SECRET_KEY=<password>
 
+If you encounter `Forbidden (403)` errors at BNL RCF, try adding the `NOPROXY` option:
+
+.. code:: C++
+
+    TFile* file = TFile::Open("s3https://dtn01.sdcc.bnl.gov:9000/eictest/ATHENA/<path>.root","NOPROXY AUTH=<login>:<password>");
+
 
 XRootD access
 -------------