Maybe related to this semi-breach?
   [1]http://yahoo.tumblr.com/post/75083532312/important-security-update-f
   or-yahoo-mail-users
   Looks like someone took a previously leaked DB of emails/passwords and
   ran it against Yahoo's servers.

   On Thu, Jan 30, 2014 at 6:19 PM, David <[2]wb8foz@nrk.com> wrote:

   On 1/30/14 2:20 PM, jim bell wrote:

     (Raising the question: Is there a reasonably straightforward
     mechanism
     to allow a disgusted user to (easily and automatically) transfer all
     of
     his emails from one system to another? Obviously, email service
     providers are motivated to try to lock in users, but maybe there's a
     way
     to fight this.)

     IMAP.
     I have IMAP set up on my Yahoo account:
     Server: [3]imap.mail.yahoo.com
     Port: 993
     Username: [4]xxx@yahoo.com
     SSL/TLS
     Then I can just transfer messages to another IMAP account.

   --
   [5]konklone.com | [6]@konklone

References

   1. http://yahoo.tumblr.com/post/75083532312/important-security-update-for-yahoo-mail-users
   2. mailto:wb8foz@nrk.com
   3. http://imap.mail.yahoo.com/
   4. mailto:xxx@yahoo.com
   5. https://konklone.com/
   6. https://twitter.com/konklone