SMTPServer @IP SERVER SMTP
SMTPRetry 1
SMTPFromName NAME SERVER where NetXMS is install

And a default value that has not been changed is the port number to send emails or 25.

From the server where NetXMS is installed I can ping the SMTP server but not resolve the name. But as I put the IP address so I don't think it's a mistake.

I saw on a Forum page (https://www.netxms.org/forum/general-support/email-test/) that the following command: nxevent -u admin -P adminpassword localhost SYS_NODE_DOWN  would allow you to send emails manually. I tried to run it from the NetXMS console while being on the server where it is installed but that puts me UNKNOWN COMMAND.

Also port 25 is well open.

Thank you for your help