[swinog] hotmail issues since 18/1 ?

Hoi zäme

I have a couple of customers complaining they are unable to send emails to hotmail - typically they see rejects such as this:

550 SC-001 (BAY004-MC5F11) Unfortunately, messages from 88.198.198.124 weren't sent. Please contact your Internet service provider since part of their network is on our block list.

It doesn't affect all customers and checking our logs, it appears to have started 18/1. Prior to that we had no problems delivering outbound mails to hotmail, since then I see 149 bounces with the message above).

The customers are on dynamic ranges from Swisscom, UPC and e.g. Virgin (in the UK). Has anyone seen something similar?