length of the query string for this request exceeds the configured maxQueryStringLength value

We use passive federation, the adfs-server is called MyADFS.MyInternalDomain and it is also exposed on the internet as myADFS.MyExternalDomain.com.

Everything works as expected when accessing it from the internet, but if I try to access
myADFS.MyExternalDomain.com from within MyInternalDomain, I get a query string of some 3-4000 characters, and the adfs webserver throws a "length of query string exceeds..".

Here's an example of the query-string.

https://myAdfs.MyExternalDomain.com/adfs/ls/?wa=wsignin1.0&wtrealm=https%3a%2f%2fMyAppServer.MyExternalDomain.com%2fprivat&wctx=rm%3d0%26id%3dpassive%26ru%3d%252fadfs%252fls%252f%253fwa%253dwsignin1.0%2526wtrealm%253dhttps%25253a%25252f%25252fMyAppServer.MyExternalDomain.com%25252fprivat%2526wctx%253drm%25253d0%252526id%25253dpassive%252526ru%25253d%2525252fadfs%2525252fls%2525252f%2525253fwa%2525253dwsignin1.0%25252526wtrealm%2525253dhttps%252525253a%252525252f%252525252fMyAppServer.MyExternalDomain.com%252525252fprivat%25252526wctx%2525253drm%252525253d0%2525252526id%252525253dpassive%2525252526ru%252525253d%25252525252fadfs%25252525252fls%25252525252f%25252525253fwa%25252525253dwsignin1.0%252525252526wtrealm%25252525253dhttps%2525252525253a%2525252525252f%2525252525252fMyAppServer.MyExternalDomain.com%2525252525252fprivat%252525252526wctx%25252525253drm%2525252525253d0%25252525252526id%2525252525253dpassive%25252525252526ru%2525252525253d%252525252525252fadfs%252525252525252fls%252525252525252f%252525252525253fwa%252525252525253dwsignin1.0%2525252525252526wtrealm%252525252525253dhttps%25252525252525253a%25252525252525252f%25252525252525252fMyAppServer.MyExternalDomain.com%25252525252525252fprivat%2525252525252526wctx%252525252525253drm%25252525252525253d0%252525252525252526id%25252525252525253dpassive%252525252525252526ru%25252525252525253d%2525252525252525252fsportprivat%2525252525252525252fdefault.aspx%2525252525252526wct%252525252525253d2011-04-06T11%25252525252525253a32%25252525252525253a26Z%2525252525252526wauth%252525252525253durn%25252525252525253aoasis%25252525252525253anames%25252525252525253atc%25252525252525253aSAML%25252525252525253a2.0%25252525252525253aac%25252525252525253aclasses%25252525252525253aPasswordProtectedTransport%2525252525252526whr%252525252525253didporten-ver1.difi.no%252525252526wct%25252525253d2011-04-06T11%2525252525253a32%2525252525253a26Z%252525252526wauth%25252525253durn%2525252525253aoasis%2525252525253anames%2525252525253atc%2525252525253aSAML%2525252525253a2.0%2525252525253aac%2525252525253aclasses%2525252525253aPasswordProtectedTransport%252525252526whr%2

What's up with all the %25-paddings in the query string?