I have spent the last couple of hours trying to get TLS working, sadly
no luck.
When I telnet and and do STARTTLS I get the error no server certs
available TLS won't be enabled.
I followed the instructions on the how to forge (the link I was given
before was a tad over my head)
The certs are all made and in the /etc/postfix/ssl/mailserver directory

as an aside - does this require a purchased security certificate to work?
Also to check I understand does the client (i.e. thunderbird) send a
request to send to the server which sends them back a key that gets
'attached' to the email that is sent which then authenticates when it
reaches the server and is allowed to be sent? Or have I got it all wrong.

Thanks
Kate