After iOS upgrades and updates, I was still able to receive emails fine but could not send them. How can I fix this?
I went to the free memory section, and saw that I had only 400MB free (of 16G). So I deleted a few apps, pics, videos etc, and then I could easily send email. Again, not sure that this will work for everybody. If your email settings were right, and everything was working right (you did not change any passwords or servers etc.), this fix may work for you.