Yahoo! definately has some reliability issues, maybe associated with so many iphones hopping onto the IMAP bus at once.
Mine has been spotty. But here are some truths:
- The first time you send/recieve email, do it using Edge.
- You can just leave the IMAP path under advanced settings to the default. The one floating around these forums isn't needed.
- Yahoo push seems to work best if it is the only mail account on the iphone, but it has worked for me with multiple accounts.
- If there is a problem with send or receive. Try rebooting the phone, then sync it, then as a last resort send and receive email by logging into your account manually via Yahoo.com. Each of these has cleared up performance issues, not neccesarily doing all of them.
- If yours never worked, delete the account under settings/mail and then regenerate a Yahoo account and ONLY enter your yahoo name and password. Don't touch advanced settings. Then, with wifi off, try a few tests. After it works, wifi is fine to use. I just understand the initial establishment of the IMAP usage on the account needs to occur via Edge or problems might develop.