VisualStudio won't accept credentials in enterprise environment - StatusCode: 0x80090308

I'm currently using Visual Studio Community 2015, Version 14.0 Update 3.

My problem is, that I can't connect to my own MS TeamFoundationServer 2015 from my workplace. The problem is definitely not missing access rights, because I can connect from anywhere except my office.

I try to add my TFS using TeamExplorer -> Connect to team project -> Servers -> Add. Then I enter my connection data (which is correct, double- and triple-checked). After that, I'm asked for my credentials as seen in this picture (URL and Username changed for the pic):

But even if I enter the correct credentials, it won't let me connect. It displays the following error:

For me, this looks like my credentials are wrong. Except they aren't. I just double checked this on a few other PCs.

The cause of the problem is probably the authentication of my company. Because if I try to open the TFS-Page in the VisualStudio browser (Ctrl + W and then W), I instantly get the following error, an usual IIS 401.

But usually I get asked for my credentials if I try to open this page, on every browser. Except on the VS-Browser.

So does VisualStudio tries to authenticate me automatically with my Windows-Credentials? If so, where can I turn this off? If not, what could be the problem?

I don't think it's because of a firewall or a proxy, because I can connect to the TFS, but just not authenticate.

EDIT for further information.

First, I am the administrator of the TFS myself.

I created the user "TfsUser" on my Server, so his full name is "WINDOWSSERVER\TfsUser". If I log in with this username (and his password), I get in without problem if I'm anywhere except my office. If I enter the credentials correctly, the Windows Security window keeps popping up (like if you misspelled your password). After about three to four (but can also be two or five) tries, the Error from Image 2 pops up.

Edit 2

I dived deeper into the issue. On my server, I saw the following entry in my security event log:

Logon Failure:

• Reason: An error occurred during logon

• Security ID: NULL SID

• User Name: TfsUser

• Domain: WINDOWSSERVER

• Authentication Package: NTLM

• Workstation Name:

• Status code: 0x80090308

• Substatus code: 0x0

With this status code, I find the following SU-Question (with no answer and no information to help me): AD DC - Error 4625 Status 0x80090308