Modify the sending address in Yahoo Mail for Android

If you’ve added more than one email address to the Yahoo Mail app, you can change your sending address when you’re composing an email without switching between accounts.

1. Tap the CC/BCC, From dropdown field.
2. Tap the From address field.
3. Tap the mailbox you'd like to send the email from.
4. Finish composing your message, and tap Send.