Problems sending email to hotmail?

[#1]

I just received an error message from hotmail when attempting to mail someone, indicating they have blocked one of plusnet's IPs.
Anyone else seeing this?
The following message to <xxxxxxx@hotmail.com> was undeliverable.
The reason for the problem:
5.1.0 - Unknown address error 550-"OU-001 (BAY0-MC4-F5) Unfortunately, messages from 212.159.7.36 weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors."
Final-Recipient: rfc822;xxxxxxx@hotmail.com
Action: failed
Status: 5.0.0 (permanent failure)
Remote-MTA: dns; [65.54.188.126]
Diagnostic-Code: smtp; 5.1.0 - Unknown address error 550-"OU-001 (BAY0-MC4-F5) Unfortunately, messages from 212.159.7.36 weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors."; (delivery attempts: 0)

[#2]

Welcome to the forum inversions
I've just sent a test email from my PN account to my Hotmail.com account ok.

[#3]

It looks like one of the outgoing mail servers is listed on a blacklist judging by the error message...
I'd suggest trying again and seeing if it goes a different route.
http://www.spamhaus.org/sbl/sbl.lasso?query=SBL116135

[#4]

Yes, in fact I retried a few times and it seems to have worked okay.
Thanks for checking.

[#5]

One of our outbound mail servers got listed by Spamhaus due to some questionable activity originating from a handful of accounts (ref: 68161). We've since dealt with the underlying problem, requested removal from Spamhaus' list and temporarily removed the affected server from service.
All should be well now.