emails from BT being blacklisted?

Had someone text me last night that an email they had tried to send me from their BT account had been bounced as the "sender was blacklisted". They tried again a few minutes later and this time it came through. Anyone else had this yesterday?

Blacklisted by who (whom ?).

The text message didn't say.

It was likely someone on your IP (or possibly IP range) had previously sent out spam and had been blacklisted. It is also possible that a core SMTP outgoing server for BT was blacklisted. These kind of things are usually resolved quite quickly when it is a major ISP who has been blacklisted.