Outlook 2016 Send from Outlook Alias Account?

I am not seeing that behavior.  I've sent from an alias to both Microsoft and non-Microsoft accounts (Comcast.net) and each had only the alias in the 'from' box.  In the Microsoft account case, both the sending and receiving accounts have the Exchange backend.  FWIW, the sending account was recently converted, while the receiving account is new enough to have been born with the Exchange backend.

The problem with this approach is the recipient sees the email sender address as a bunch of letters/numbers at outlook.com on behalf of correct email address instead of from correct email address. Doesn't look good - maybe OK for kids and no-professionals but not for businesses with their own domains.

Also, in my case, I have an Office 365 Outlook account for work as well as 2 Outllook.com accounts for personal. Even if you set the personal accounts as default send from in Outlook desktop, the work account is always used for Sent Items (even if the email address in this case is the personal account). And then you can't move the personal email from the work sent items folder into the personal one because Exchange Active Sync does not support that!

It seems Microsoft have found every possible way to run multiple accounts and turned the all off out of spite.

I get so furious with Microsoft. Having wasted hours looking for a solution that will allow me to create aliases on Outlook 16 I cannot find any easy solution. Creating different e-mail accounts just creates lots of clutter and wasted time when all I want to do is have ONE inbox yet have the facility to use different e-mail personas for sending and receiving for the different aspects of my business. For a multi-billion dollar company it reflects poorly on the needs of its clients.

You actually create the aliases via your online account.  (This assumes it is a Microsoft account - outlook.com, live.com, or Hotmail.com)  Sign into outlook.com and create your alias via the "Settings" gear icon, "Connected Accounts" item.  Create your desired alias(es).

At this point, when you go into Outlook 2016 and compose a new message (or reply to an existing one), your "from" button will be a dropdown list of the accounts which can be used to send the mail, including the alias(es) added on outlook.com. 

At least, that's how it works for me.

I get so furious with Microsoft. Having wasted hours looking for a solution that will allow me to create aliases on Outlook 16 I cannot find any easy solution. Creating different e-mail accounts just creates lots of clutter and wasted time when all I want to do is have ONE inbox yet have the facility to use different e-mail personas for sending and receiving for the different aspects of my business. For a multi-billion dollar company it reflects poorly on the needs of its clients.

I have no problem selecting an alias but it just ignores what I select and uses the default address anyway.