Freecycle bouncing

[#1]

Can anyone tell me what's changed recently that's causing emails from Freecycle to be bounced?
Yahoo groups say this
Remote host said: 552 Spam Message Rejected [BODY]
roughly 70-90 per week which disables the emails
I can re-enable them from the Freecycle group page but they get bounced again after a few days. I don't know what the problem is because nothing ends up in the spam folder.

[#2]

Topic getting a few Undeliverable responses is concerned with emails containing links to freecycle groups being rejected when attempting to forward but I think the discussion in that thread might well be relevant to the current problem.
David

[#3]

ditto, and this is getting really irritating. I'm going to raise a ticket.

[#4]

Is there any news on this?
I am (eventually) getting the following bounce message whenever I try to send to ANY of my Yahoo Groups:

Quote

A message that you sent to the following recipient could not be delivered due to a permanent error. ** The remote server 98.137.34.115 responded with: ** freecycle-exeter@yahoogroups.com 420:Socket error This message was created automatically by mail delivery software on the server avasout02.

The responding remote server is the same whichever Group I'm trying to send to....
I don't think the other thread is helpful?  Any ideas?
Thanks
Chris