The long-requested ability to send emails from an alias in Office 365 has been finally released!
When you use an alias to send an email, the From and Reply to field for the recipient will appear to be the alias meaning the recipient will only see the alias and not your primary email address.
To make this happen, simply login to your Office365 tenant via Powershell and run the following command:
Set-OrganizationConfig -SendFromAliasEnabled $true
That’s it! Within a few minutes it should begin working.
To send from the alias, make sure you are showing the From field by clicking Options > From, shown below