When you reply to any email from the Outlook app, you automatically reply with the default account . If you have more than one mail account while using the application, you will automatically reply with the default account both when sending and replying. You can simply change the default mail account. You can do this by following the steps below.
Outlook Default Account Change
The process we explained in this article is valid for Outlook 2010, Outlook 2013, Outlook 2019, Outlook 2016 and Office 365.
1. Open the Outlook desktop application.
2. Click the File tab. Switch to the information tab.
3. Go to the Account settings tab, then select the account settings section again.
4. The mail accounts used in the Outlook application will appear on the page that opens . To change the default account, click on the mail account and click the set default link and close it.
This way you can change the default email account. If you wish, you can add a new e-mail address from the same place and make the default account. You can click on the new tab for this.