Currently Being ModeratedDec 17, 2013 9:04 PM (in response to Kellie McGilvra)
You need to use the Software Update feature first because they just released a Mail fix of some sort yesterdaay.
http://support.apple.com/kb/HT1277 Then see if this helps.
Currently Being ModeratedDec 18, 2013 6:20 PM (in response to Donald Morgan)
I ran the updates the other day via the app store, and just did it again tonight. Everything is up to date, and as of tonight, I still can't send via mail using my yahoo account. Yet the messages still download fine.
I've had this happen on and off int he past, but usually within a day or two or after a restart it fixes itself, but no so luck so far.