The Problem

On December 8th the group operating the free NEOS service announced on Twitter that from January this year users are required to provide a valid email address for all job submissions to NEOS.

https://neos-guide.org/content/FAQ#email

Unfortunately, this change affects GAMS users who submit NEOS jobs via Studio. We are working on resolving this issue with the coming release of GAMS 34.

Temporary fix

As a workaround you can submit jobs via Kestrel instead of directly via GAMS Studio, and provide an option file kestrel.opt. Provide your email in this file with the keyword email, as in the example snippet below:

$echo email jdoe@jeangreyhigh.edu > kestrel.opt  
$echo kestrel_solver cplex >> kestrel.opt
mymodel.optfile = 1;  
option solver=kestrel;  
solve mymodel using lp minimizing obj;  

This solution might not work in all circumstances though, because with Kestrel the GAMS execution phase happens locally, so you might run into license related limitations. For more information you can read this blog article. .