smtp server is not responding check your outgoing mail server?

The issue may not be the server your thinking of in some cases. If you have multiple emails set up, it could be one of the other emails smtp setting that are wrong so check those also.

When you send or receive mail it goes thru each account you have set up each time to send or receive. Any setting issues with any of these account can stop all mail in or out.

Even of the setting tells you that this information is option, fill in your username and password in the outgoing mail server setting.

Settings>Mail, Contacts, Calendars>Your email account, go into Account, then SMTP (under Outgoing Mail Server) and try filling in your username and password.

Who is your email provider?

If you already have the email account set up on your iPad, this issue (your issue) does not typically need to have the host name added or changed?