Making Outlook aliases work within iOS mail.

Hello,

I've been trying to set up an alias within the iOS 9 mail app. Everything works fine, even sending the mail after selecting the alias but when the mail is received, it appears that the main address has been used instead of my alias.

The main address is an @hotmail.com (Outlook) address but the alias is from another private domain. I've setup the account in my iPhone's settings using IMAP and it only fails when using Apple's mail handler. I've tried with the Outlook app and there it works.

Could someone help me fix this issue?

Thanx!