Does Ecto.Adapters.Tds support domain logins?

I have a config like:

config :my_app, MyApp.Repo,
  username: "domain/user, 
  password: "password", 
  database: "database", 
  hostname: "hostname

MyApp.Repo is using the Tds adapter that comes packaged with Ecto.Sql. I’m troubleshooting a correction error and it has been suggested that the adapter may not support domain logins.

I can’t confirm or deny it from looking at the documentation on hexdocs, does anyone know for sure?

No, that isn’t currently supported.
You have to use the SQL Server Authentication with a local MSSQL account.