OK - a couple of questions to help us understand your problem.
Can you tell us what your email settings are?
'Settings', 'Mail, Contacts, Calendar', 'Account', <--the account that you're trying to send from -->, and then the settings relevant to sending mail under the SMTP entry. Obviously don't send us your account name or any passwords.
Also, when you say that you can't send mail, what exactly happens when you try to send mail? Are you on your home network presently or away from home and just logged on to the Internet from somewhere else?
And --- welcome to iPad Forum...
Tim