Hi -
I had same problems, but got Yahoo! mail to work on my new iPhone5 by deleting the old Yahoo! mail account and setting up a new mail account by inputting the information below for a new Yahoo! imap mail account. Make sure to go to "Add Account" and choose "Other," not the Yahoo! template, then input your Yahoo! email information. It worked for me!
How to set up IMAP on your mobile device
ID: SLN3361Refers to: Mobile Mail , Mobile
Description
This article explains how to configure your mobile device to use Internet Message Access Protocol (IMAP).
Resolution
To set up Internet Message Access Protocol (IMAP) on your mobile device, please use the following settings:
Incoming Server - imap.mail.yahoo.com
Outgoing Server - smtp.mail.yahoo.com
Incoming Port - 993 (requires SSL)
Outgoing Port - 465 (requires SSL/TLS)
User name: full email address (for example,
bill@yahoo.com or
bill@rocketmail.com)
Password: the password you log in to Yahoo! with.
Note: If your Yahoo! Mail address does not match your Yahoo! ID, you will need to use the beginning of your Yahoo! Mail address when you set up your client. For example, if your Yahoo! Mail address is "jim@yahoo.com", but your Yahoo! ID is "james", you will need to use "jim" as your user name when setting up the IMAP client.
If you are having trouble setting up IMAP on your mobile device, we would recommend reviewing your phones instruction manual or contacting your mobile provider.