Connection to localhost:25 refused

[Alisdair McDiarmid <alisdair@letdown.demon.co.uk>]

I've just upgraded to potato fully, with exim 3.02, and now I
can't connect to port 25 on localhost:

[root:~] # telnet localhost 25
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused

Obviously, fetchmail now doesn't work, and I can't receive mail
via SMTP either. I've checked /etc/exim.conf for anything obvious
but I can't see anything blocking connections.

Can anyone help me please?
-- 
alisdair mcdiarmid               alisdair@letdown.demon.co.uk
[your home may be at risk if you do not keep up repayments on
 your loan. any and all advice given is strictly confidential]