I cannot to connect to IMAP server, any ideas?

I have a macbook air and can access my email by signing onto the cloud but can't send emails via my Mail outbox. It keeps asking me for a password.
Connection doctor says "could not connect to this IMAP server. Check your network connection and that you entered the correct information in the Account preferences. Also verify that the server supports SSL. If it does not deselect the "use SSL" checkbox in the advance tab of account preferences"

So my question is? what is the correct information required for the account preferences and how do I know about SSL? ( What ever that is!)

Thanks in advance and hoping this is an easy fix.

Lianne