Append or Inject domain into Username when logging into sharepoint 2013

Question

I have set up SharePoint 2013 for my organization but the users have to always enter a domain (User1@domain.com) after their username.

I have searched but i cant find any solution or even where the file for this is located. I'm wondering if i can get some help either finding where that file is or an alternate solution for this issue. Thanks!

Switching my authentication type is not really an option either, and yes I want the user to be promoted for the password every time.

Answer 1

On the SharePoint server I went to IIS, clicked on the local host tree then in the center console under IIS I opened up Authentication. Click basic authentication then under actions click edit. Once there I entered a default domain name and voila, like magic it now works!

Answer 2

So if i understand correctly here your SharePoint farm domain (eg sharepoint.com) and users domain (user@companyXYZ) don't have a "trust relationship?.

When you access a office document from a library as an Untrusted Client (even though your login credentials are already authenticated by the browser session cookie) when an Office Application opens, IE does not pass authentication/trust/token to the next application to gain the same access that is already trusted with IE. The additional log-in prompts is because the documents opened with Office are trying to re-establish a trust per application, because the client machine is not trusted from a public web and a new authentication is requested.

May want to review : Authentication prompts when opening Microsoft Office documents

If you can provide a fiddler trace of an authentication and identify if you are using "classic" or "claims" i can help more.