i picked up the issue after upgrading to IOS 5.1.1 and yahoo's email issues on 6/19. I manage an IT dept so I'm not some country bumpkin (no offense inteneded) Telling me to check my settings and reboot isn't really going to solve anything when i've checked them a dozen times Apple's support response is weak at best and Yahoo's well there is a reason Google is kicking their butt.
I also have Gmail, Hotmail, Windows Live and MS exchange accounts goign to my phone and they are working without issue.
Pretty much tried same as everyone else. i've nuked and restored phone, email accounts blah blah blah...... getting various errors including
can't connect to server
wrong password
apple.imap.yahoo.com not responding and
wrong password logging into apple.imap etc
every once in a while things sync up (like about 10 hours ago)
I have a sneaking suspicision that the trust relationship between apple.imap.yahoo and the actual yahoo mail servers is borked. Would explain some of the errors. I've seen similar type stuff with Exhange between 2 domains.
Perhaps if anyone could get through to Apple and/or Yahoo's support engineers they could have them look at it.
other than that I'm open to any other suggestions people have. Yes my phone is a dinosaur Iphone3G - but it worked fine till i updated the IOS and yahoo mail went down last week for a while