I took a screenshot image of my mail so you could see what version I have. Sorry thought there was a way to upload an image here, but apparently not.
Wow, I see this was originally posted in Oct 2012 - Now it's Oct 2019 7 years later with this same issue of double spacing. This is happening in my Draft folder after the 2nd line was entered. I'm on the regular version of Yahoo Mail. Not Beta or Plus. It's still happening 7 years later again. Doesn't 7 years happen to something of bad luck? Who knew. Maybe Yahoo Support imposes this issue to protect their employment from being cut.I am using the New Yahoo Mail Beta. When composing an email previously each line was single spaced. Today, for no apparant reason, the spacing has changed to double space. I am unable to find anywhere to select spacing and get it back to single space. Any suggestions?