On the left pane, selectMail.
ChooseGmailfrom the right pane underConnected accounts.
There are two options:
To add Gmail as a send-only account, go for the second option above.

Heinz Tschabitscher
SelectOKon the Outlook.com page that shows the confirmation explaining that you successfully connected your Gmail account to Outlook Mail.
When it’s finished, you’ll see it change to “Up to date.”
UnderSet default From address, use the drop-down menu to choose your Gmail account.

SelectSAVEto make your Gmail account the new default “send as” address in Outlook Mail.
Doing this will only change the default email address for new emails.






Heinz Tschabitscher