| Overview | Opening in a Web Browser | Opening in an Email Application | Forwarding Mail to Another Account |
You can forward your incoming Yahoo! Mail Plus messages to another email address—even another Yahoo! Mail address. If you have more than one email account, forwarding lets you receive and work with all of your messages in one location.
While your email is being forwarded, new messages won’t appear in your account on the Yahoo! Mail server. (Messages that came into your mailbox before you turned on email forwarding remain in your account.) This means that you can’t read new messages using a browser at the Yahoo! Mail website. (Of course, if you’ve forwarded to another Yahoo! Mail address, you can read that mail at the Yahoo! Mail site.)
Notes:
You can’t use an email application (as described in the Opening Yahoo! Mail Plus in an Email Application)
and forward your email at the same time.
Yahoo! Mail Plus doesn’t apply filters to
your forwarded mail. 
(More Details)
In a Web browser, go to the POP & Forwarding page. (Remind me how.)
On the POP & Forwarding page, make sure that the Forward your Yahoo! Mail option is selected.

Enter the email address to which you want to forward your Yahoo! Mail.

Click Save Changes.

The Verify Email Address window opens. You must verify that you are the owner of the email account you entered before you can forward email to it.
In the Verify Email Address window, Step 1, click the blue Send Code link.

Yahoo! Mail sends a message containing the verification code to the email address shown in the window (that is, the address that you want to forward your Yahoo! Mail to).
To complete the verification process immediately:
Go to forwarding mail account and look for a message from Yahoo! Member Services.
Note the confirmation code in the message.
Enter the confirmation code in the box in Step 3 of the Verify Email Address window, then click the Done button.

Yahoo! Mail confirms that you’ve successfully verified the account.

Tip: You can also follow the instructions in the email message to complete the process.
If you prefer to complete the verification process at a later time:
Click the Verify Later button.

Yahoo! Mail confirms that you must still verify the address before you can forward mail to it.

At a convenient time, check your external mail for a message from Yahoo! Member Services.
Follow the instructions in the email message to complete the verification process.
To turn off mail forwarding, return to the POP & Forwarding page and select the Allow your Yahoo! Mail to be POPed option instead of the Forward your Yahoo! Mail option.
Of course, you can forward your external email accounts to your Yahoo! Mail account and manage it all through the Yahoo! Mail website. We cover this in the Using Other Email Accounts With Yahoo! Mail tutorial.