Unable to email to users@lists.roundcube.net

[jlbrown]

I’m trying to post to the users mailing list but get a message saying that there is a server configuration problem at mx.kolabsys.com :

Code: [Select]

2023-06-26 19:13:31 users@lists.roundcube.net R=dnslookup T=remote_smtp defer (-44) H=mx.kolabsys.com [212.103.80.151]:25: SMTP error from remote mail server after RCPT TO:: 451 4.3.5 Server configuration problem
2023-06-26 20:14:04 H=mx.kolabsys.com [212.103.80.150] SMTP error from remote mail server after RCPT TO:: 451 4.3.5 Server configuration problem
Anyone know to go about getting this fixed?

James.