Outlook 365 does not let you enter mail username?
When try to add a new email account to Outlook 2016 or Outlook 365, the default "Wizard" does not allow you to enter a username of the IMAP/POP3 server.
To run the setup with all account options without the Outlook wizard, follow these steps:
1. Navigate to: File > Information > Account Settings > Manage Profiles
2. Open "Email Accounts", choose "Setup your account manually"
3. Enter your mail server info, username/password and choose "More settings"
4. Under "Outgoing server", you may have to check "Outgoing server requires authentication" in most cases ("Use same settings as my incoming mail server"). Modify ports if necessary under the "Advanced" tab.