Can't add DreamHost email account to my Mac Mail

I've got a new email account from DreamHost and I want to add to my Mac Mail. When I followed the path: Mail -> Add account -> Other Mail Account -> enter username, email, and password, then I suppose to be able to click "Sign In" button to continue with the configuration. However, the "Sign In" button is always greyed out.

Does anyone know how to fix this issue?