Autodiscover asking for user name

Hello everyone,

Im having problem to make autodiscover work properly with iPhone. If I try to setup an external user on the Outlook, autodiscover works great. However when I try to setup an iPhone, I type the email and password and then when I press next, the user name will be blank. If I type the user name, it will finish to setup the email. Is that right? Shouldn't autodiscover setup everything automatically? 

Thanks

Flavio Ribeiro