We are currently investigating a problem affecting the sending and receipt of messages to customers' mailing lists:-
http://www.plus.net/support/email/mailboxes/mailing_lists.shtml

Administrative commands, subscription requests and messages sent to a list may not be getting delivered.

Our network engineers are investigating and further detail will be provided as it becomes available.

Please accept our apologies for the inconvenience.

Kind Regards,

Bob Pullen
Customer Support