Getting message that the browser I am using is not compatible with the webmail service I am trying to log into

[jnelsoninjax]

I am using the newest version of Firefox and when I try to go to gmx.com I get this message:

It's generally not an issue since I use Thunderbird to retrieve my email, but every once and a while spam sneaks in and I have to go to the web interface to mark it. I can access the site in edge with no issues. What could be causing this to happen?

[Onikwuthkro]

Probably due to the plugins you use, do you use any plugins?