You can
transfer Outlook emails to Yahoo Mail manually by setting up both accounts in Outlook using IMAP. Here’s how:
1. Open Outlook and go to File > Add Account.
2. Add your Yahoo Mail account using IMAP settings (Yahoo's IMAP server: imap.mail.yahoo.com, port: 993).
3. Once configured, your Yahoo account will appear in the Outlook sidebar.
4. Drag and drop the emails or folders from your Outlook mailbox (PST file) into the Yahoo Mail folder.
The process is complete!