Sadly, you are not able to send or receive messages in Yahoo? If your answer is yes, then you need to check settings in your email account.
Incoming Mail (IMAP) Server
Server - imap.mail.yahoo.com
Port - 993
Requires SSL - Yes
Outgoing Mail (SMTP) Server
Server - smtp.mail.yahoo.com
Port - 465 or 587
Requires SSL - Yes
Requires authentication - Yes
Check the proper settings of IMAP and SMTP in your Yahoo email account.
