My iPad 4 has worked quite happily until I recently changed my btinternet email password.
The pad collects my email happily but I cannot reply to received email on the iPad.
I have updated my email password on the iPad but what do I have to do to enable me to get the iPad to send or reply to emails?
Your iPad doesn't know the correct SMTP server details to use for your outgoing mail. Follow the instructions here
http://www.serversmtp.com/en/smtp-settings-ipad
ensuring that Host Name (under 'Outgoing Mail Server') is set to show
mail.btinternet.com
If Buenchico's post doesn't work
Have you changed you password on your laptop or in your iPad? If you have just changed it on your laptop you may need to go to settings, mail,contacts,Calender and also change it there. Or do a reset through settings which will reset your iPad and only takes you passwords off everything.
I don't think that my brain can have been properly in gear when I posted above. Everything I wrote is correct but the one thing I forgot to suggest is to retype your password within the SMTP server settings. (Given that it was changing your password that caused your problem in the first place, that should have been top of my list!)