I am trying to set up a mail server which I can access remotely. I am using sendmail on a FC4 box, and my understanding is that I should use an IMAP server rather than Pop3.

It also means that I need to have authentication working. So far I have created a sendmail.pem certificate, but I am unable to get my Outlook client to log into my mail server as it doesn't seem to recognise my user name and password. It continually opens a pop-up asking me to enter those details.

I also have an error in my maillog file which says
STARTTLS: CRLFile missing

I haven't been able to find much documentation about what I need to do to get this working. Can anyone point me to some straight forward documentation which will help me get this up and running?

Not quite sure of my ground here, but I was of the opinion that there is a difference between using certificates for secure connections (eg SSL ) and authentication. Secure connection encrypt the connection, authentication is verifying the user attaching to the server.

What IMAP server are you running (and no, sendmail isn't an IMAP server)? FC4 comes with Dovecot included which is pretty simple to set up.

Are you trying to log in from the internet or just from a different machine on the same local network?

Hooking up from Outlook should be a piece of cake. Just follow th instructions under Tools -> Email Accounts

Worry about the details such as secure connections later - get the basics working first