| Overview | Adding Another Account | Sending Mail Using Another Email Address | Receiving Email From Another Account | Editing an Account | Deleting an Account |
With just a click, Yahoo! Mail checks your external email account for messages and pulls them into your Yahoo! mailbox. Once the messages are in your mailbox, you can organize them into different folders and treat them as you do any Yahoo! message.
Notes:
Yahoo! Mail fetches messages from your external mail accounts
only when you request it. It doesn’t automatically retrieve external
mail when you check your Yahoo! Mail account for new messages.
If you created filters, Yahoo! Mail can
use them to sort the mail you receive from the external account. 
Follow the procedure for adding a non-Yahoo! email address for receiving email. (Remind me how.)
Be sure that you’ve verified that you own the non-Yahoo! mail account. (Remind me how.)
Once you have verified the account, its mail server appears in the Check Other Mail area above your folder list on the left side of the Mail page.
Click the name of a mail server under Check Other Mail to retrieve messages from that server.

Tip: Clicking the Check Mail button above Check Other Mail does not retrieve messages from your external mail accounts.
Yahoo! Mail retrieves messages from the selected server into the Inbox (or other mail folder) of your Yahoo! Mail account and marks the messages with the indicator color you selected when you set up the account.

When you reply to a message retrieved from a non-Yahoo! email account, Yahoo! Mail automatically uses the return address associated with that account. For example, if you respond to a message retrieved from the rmiller@atwork.com account, the response’s default "From" address will be rmiller@atwork.com.
To use a different return address for your response, select the one the From menu on the compose page, as described in Addressing Your Message.