I'm hoping you're on Orange UK (i work there so these tips should help)
Is it an "XXXXXXXXXXX@orange.net" email address??
Tap "Settings"
Tap "Mail, Contacts, Calendars"
Under Accounts tap "Add New" then "Other"
Name = Your Name
Address = Your Email Address
Password = Your Email Address Password
Descrion = Your Choice
It wont be able to auto fill the settings and will bring you to the New Account page.
make sure you select "POP" at the top
Incoming Mail Server = pop.orange.net
Username = your login information
Password = [should already be filled with dots]
Outgoing Mail Server = smtp.orange.net
Username = [leave blank for now]
Password = [leave blank for now]
If you get an error regarding SSL, you should select YES to try again without SSL.
It's very important that you have your APN (access point) set to
orangeinternet
One Word & Lower Case
To check this follow
Settings > General > Network > Cellular Data Network
APN = as above
Username & Password should be left empty
It will now verify and you should be setup correct after this.
Let me know if this helps at all