How to set up an e-mail address in outlook hosted by an external domain

I have an outlook account with a hotmail address.  I have just set up a work related e-mail account on an external domain and have tried to get it to link to my outlook account by setting up an alias with the same address.  However I have not received the test e-mails I have sent.  I did note on one of the setting pages that the external domain account was send only and not receive, but there appeared to be no option for two e-mail addresses to be received on the one outlook account.  Have I misunderstood something??