Unfortunately, Outlook 2016 can not deal with alias identities (as opposed to Thunderbird). It is, however, possible to replace your Posteo address with an alias address in Outlook 2016. This makes sense if you only wish to send and receive emails using an alias address.
Setting up a Posteo email alias in Outlook 2016
If you have already set up your Posteo account (main address) in Outlook 2016 and would instead like to use your alias address, you can replace the sender with your alias as follows:
- In the main window of Outlook 2016, click File
- Click Account settings
- Click Account settings
- Select your Posteo account
- Click Change…
- In the Email Address field, enter your email alias.
Tip: You can also change your name in the Name field - Click Next
Outlook will now test the connection settings. Complete the setup by clicking finished.
You will now always compose emails using your email alias. Your main Posteo address remains unknown to recipients of the emails.