Okay well when I first tried using Yahoo email on my droid it didn't work...so I tried this solution I found:
Go to manual setup > IMAP account and change to these settings....

Imap server - imap.mail.yahoo.com
port - 143
security type - none

SMTP Server- smtp.mobile.mail.yahoo.com
port - 25
security type - none
* check Require sign-in

And, wow it started working...for a bit. Right after I had set that up I started installing my invisible shield I had purchased and had to turn my phone off, after I was done I turned it back on and didn't touch it again for 8-9 hours so the shield could air dry. When it was done I tried refreshing my e-mail because I hadn't received any since I set up the yahoo e-mail using that method and thought it was strange. So when it was refreshing it stopped and displayed a little message on the top that said "username and password is incorrect"....not this again...so now I'm at a loss on what to do. Any suggestions? Thanks.