One NethServer environment cannot send email

There was the same error in another thread: Nethserver 8 Not accepting any email - #15 by derilium

Let’s check if the port is open:

[root@ns8rockytest ~]# ss -tlp | grep 11332
LISTEN 0      4096       127.0.0.1:11332               0.0.0.0:*    users:(("rspamd",pid=10741,fd=67),("rspamd",pid=9502,fd=67))

You could try to restart the rspamd service/container:

runagent -m mail1 systemctl --user restart rspamd