Hello, Valeriemitchell.
Thank you for the question. Since you are able to access your email account on other device, this issue could be related to a security feature offered by your email host. Without knowing which email host you use, I will include the best resources that I can. Below, I have included two e-mail troubleshooting articles. The first article covers basic email troubleshooting. The second article will assist you if the email account you are experiencing issues with is a Gmail account.
iOS: Troubleshooting Mail
http://support.apple.com/kb/ts3899
iOS: Gmail account will not connect to Gmail server
http://support.apple.com/kb/TS3058
Hope this helps,
Jason H.