Error sending test: 550 I cannot deliver mail for some email about listmonk HOT 4 CLOSED

Thanks for your help knadh.
So if anyone wants to use poste as mailserver, here is how to integrate listmonk to poste:
1- login to admin dashboard of poste
2- go to 'system settings'
3- in the 'Relay networks' part, add this as the ip: 172.17.0.1
done.
Many Thanks to knadh for his help. without his kindness I never could solve the issue.

from listmonk.

Looks like your SMTP server is explicitly blocking e-mails (error 550). Possibly some whitelist / blacklist / spam configuration that you'll need to look at.

from listmonk.

Thanks for your response
After some time and ip of server to whitelist, I encounter with a new error:
Error sending test: EOF
What does this mean?

from listmonk.

EOF would mean that listmonk's connection to the SMTP server is closed or reset. Have you tried restarting?

from listmonk.