One of our initial premium features was that the premium server was located in a bunker in Switzerland. Unfortunately, our hosting provider decided to stop this feature and moved all their server to a “basic” datacenter in Switzerland.
Around the same moment, we were discussing implementing a more advanced and robust infrastructure that would allow us to expand and properly grow ImprovMX in a bigger service. Their decision to drop the bunker offer became apparent for us that it was time to redo the infrastructure.
We decided to move all the users, free and non-free under the same roof, but with powerful servers to handle the load. This move was made in October 2019 and has been very efficient.
But we kept our premium users in mind, and the feature set moved to a “faster priority queue” for them. All the emails are in the same queue, but premium users are treated first.
That’s why since October 2019, the mxs1.improvmx.com and mxs2.improvmx.com servers now points to mx1 and mx2 respectively. As of January 2020, we started stopping mentioning mxs servers, and since February 2020, we started marking the domains as invalid for those who still use mxs.
So if you are still using mxs servers, and received a notice, we hope this article made sense to you and that you'll be able to update your MX records back.