email to hotmail and bt internet

[Magic Foundry]

For the last three or four days all emails sent to either hotmail or bt internet addresses have bounced back. We've never had any problems before and I haven't changed any settings as far as I know. We use Thunderbird as our email client and I'm wondering if anyone else has had a similar problem with these addresses or is it something wrong with our security settings etc, or even is it possible that we have a virus that theses email servers are picking up on and refusing to accept. Any ideas would be much appreciated.
Also how do I send mail to <postmaster>.
This is the message that we get back each time.

This is the mail system at host gremlin.idnet.net.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<*****************@hotmail.co.uk>: delivery temporarily suspended: connect to
    127.0.0.1[127.0.0.1]: Connection refused

Reporting-MTA: dns; gremlin.idnet.net
X-Postfix-Queue-ID: F24301485E3
X-Postfix-Sender: rfc822; **************@idnet.com
Arrival-Date: Thu,  1 Jul 2010 08:27:41 +0100 (BST)

Final-Recipient: rfc822; ***************@hotmail.co.uk
Original-Recipient: rfc822;**************@hotmail.co.uk
Action: failed
Status: 4.4.1
Diagnostic-Code: X-Postfix; delivery temporarily suspended: connect to
    127.0.0.1[127.0.0.1]: Connection refused

[Glenn]

Send it into support

[Magic Foundry]

Thanks Glenn, although I can see I should have read the post above first.

[Simon_idnet]

We pointed out to Microsoft Hotmail that they've blacklisted us due to spam caused by Microsoft Windowx XP deficiencies. They failed to see the irony.

[Steve]

That would require a sense of humour

[Simon]

Also being discussed here:

http://www.idnetters.co.uk/forums/index.php?topic=21083