Last updated: February 8, 2017
If Outlook is connected to a primary Outlook.com account that is also connected to other secondary non-Microsoft accounts (such as Gmail, Yahoo, etc.), when sending an email in Outlook, you are not able to choose the other secondary connected account as the "From" sending account.
If you manually type in the secondary connected account email address in the "From" field, the email is sent as "On behalf of" your primary Outlook.com account.
Outlook supports sending from a secondary connected account for Microsoft owned domains such as @outlook.com, @live.com, @hotmail.com but has not implemented this functionality for third-party domains.
The Outlook team is listening to your feedback and investigating adding this functionality to future updates. Please vote up the request and add any feedback on UserVoice: Option to make Microsoft Outlook 2016 work with Outlook.com connected. In the meantime, please use the following workaround:
You can also add the secondary connected accounts (Gmail, Yahoo, etc.) in Outlook.com as additional accounts in the Outlook profile.
In Outlook, choose the File tab.
Under Account Information, choose Add Account.
On the Auto Account Setup page, enter your name, email address, and password, and then choose Next.
Note: If you receive an error message after choosing Next, double check your email address and password. If both are correct, see the next section.
For more information, please see Outlook email setup.
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