One of the more unhelpful strings around, but since this pops to the top of Google searches, wanted to provide some information that could allow people to work around this issue if they read this string.
From reviewing the posts on other sites there is currently an issue ongoing with individuals with new iPhones not being able to connect to Yahoo Mail using the Yahoo specific email setup option. Here's a string on that topic with many new iPhone users who've had this issue in the past few days. http://answers.yahoo.com/question/index?qid=20120921125258AAZ4maT
My added contribution to this issue is that I've replicated this issue with other devices running iOS6, in fact, and not just new devices. On devices I've been using to access yahoo email for some time, they continued to get Yahoo Mail just fine after I upgraded to iOS6. However, if I now delete that working account and immediately try to re-add it using the Yahoo specific option my other devices (iPad3, iPad2, iPhone 3GS, and iPhone 4) all start to exhibit the same symptoms.
Interestingly, like in the link above, I am able to get to my Yahoo email accounts by avoiding the Yahoo specific setup option and instead choosing "Other" when setting up email. Here's what does seem to work.
1.) Delete the yahoo mail account on your iphone/ipad.
2.) Add mail account using "other" instead of "Yahoo!" and setup as IMAP account.
3.) Use the following information:
- username MUST include @yahoo.com at the end
- incoming server = imap.mail.yahoo.com
- outgoing server = smtp.mail.yahoo.com
- always retype your password
Obviously, this demonstrates something is broken in the initial account set up process for the Yahoo specific option in iOS6 that isn't broken in the "Other" email process when it's set up manually.
One option is that Yahoo's servers aren't accepting authentication properly from the iOS device trying to verify the account information. However, since Yahoo's servers *do* accept authentication from the "Other" email setup process, it seems unlikely to me that Yahoo's servers would treat these IMAP requests from the same device differently.
A plausible (and I think likely) option is that there is broken Apple code in the Yahoo specific email setup option that isn't broken in the "Other" email setup code. Perhaps something changed in Apple's code for the Yahoo specific setup option that causes it to send out malformed requests or not handle return authentication confirmations properly? Don't know.
Regardless, seems to me this isn't as clear cut a case as "It's a Yahoo problem" at least with the current manifestiation of this issue.