[Hampshire] [Software] Postfix Configuration Problem

I am just trying to troubleshoot some errors I see repeated within my
mail log, this extract being based on one particular message's path
through the system:

root@bender:~# grep 8A8581B40F6 /var/log/mail.log
Jan 13 10:44:05 www postfix/cleanup[6155]: 8A8581B40F6:
message-id=<20070113104405.8A8581B40F6@???>
Jan 13 10:44:05 www postfix/qmgr[6147]: 8A8581B40F6: from=<>, size=3169,
nrcpt=1 (queue active)
Jan 13 10:44:05 www postfix/smtp[6153]: 8A8581B40F6:
to=<root@???>, relay=none, delay=0, status=deferred
(connect to mail.funkygibbins.me.uk[81.2.99.91]: Connection refused)
Jan 13 11:00:45 www postfix/qmgr[6147]: 8A8581B40F6: from=<>, size=3169,
nrcpt=1 (queue active)
Jan 13 11:00:45 www postfix/smtp[6228]: 8A8581B40F6:
to=<root@???>, relay=none, delay=1000,
status=deferred (connect to mail.funkygibbins.me.uk[81.2.99.91]:
Connection refused)

The only thing I can think of is that a connection to 81.2.99.91 (my
static IP assigned by my ISP) from my LAN goes to my router*, whereas a
connection to the same IP address from the outside world is NATted
through to the mail server.

Telnetting to mail.funkygibbins.me.uk on port 25 from the mail server or
any other host in the LAN gets the expected response from the mail
server, i.e. a connection that eventually fails.

Any ideas as to where I might start looking please?

Sean

* going to the default port gets a response from the CLI of the router