Yahoo changed some back-end settings on what mail server people can
access. If you have a free yahoo account, please be sure to modify the
settings to:
1. Email/Password
2. Manual
3. IMAP
4.
Incoming:
android.imap.mail.yahoo.com
Port: 993
Secure connection box should be checked
Outgoing:
android.smtp.mail.yahoo.com
Port: 465
Secure connection box should be checked