Ihave set up an email account, yet when I try to reply to an email it says I need to set up an account!

question is in the title!

Hello Paul,
can you please copy the error message? Is perhaps only your SMTP server missing?

If your server’s autodiscover is not set correctly, you might have to configure your account manually.
Go to Tools>Accounts, choose New account but instead of the Automatic setup choose Mail>Other.
Set up your account manually as either POP or IMAP using a correct mail server addresses.