This is what the Geniuses at Yahoo have to say about the problem...
I had sent them a link to this thread so that they could realize that lots of users had this problem and not just me...
"Please visit the URL and follow the troubleshooting steps:
http://help.yahoo.com/l/us/yahoo/mobile/comms/mail/iphone-04.html
Additionally, if the steps on the help page did not fully resolve your
issue, I'd suggest the following these additional steps to continue
troubleshooting.
- Set up your Yahoo! Account on your iPhone using the "Yahoo!" option.
Please make sure that you enter your new password when setting up the
account.
- Make sure that your iPhone is not set to Manual Push. To verify this
please take the following steps:
- Open Settings - Select Mail - Select Auto Check - Ensure it is not set
to "manual"
Regards,
Chris"
I also asked them for the Yahoo IMAP server settings and they asked me to contact my mobile service provider!!!
"Hello Rahul,
Thank you for writing to Yahoo! Mobile.
I'm sorry but the information you are asking for is not something that
Yahoo! can provide. IMAP server information is specific to your carrier.
You should be able to find the answer to your question by going straight
to your carrier. They're the real experts on their own stuff, and can
give you the most complete information on their products and websites.
Please write back to us if you have questions or comments about any of
our Yahoo! services. Good luck!
Thank you again for contacting Yahoo! Mobile.
Regards,
Eve"