Que veut dire this is the mail system at host

A classic error message!

"This is the mail system at host" is a message that typically appears when your email client or a mail transfer agent (MTA) is unable to deliver an email to its intended recipient.

Here's what it usually means:

  1. The email client or MTA is trying to send an email to a recipient's email address.
  2. The email client or MTA is unable to find the recipient's email server or the server is not responding.
  3. The message is being sent back to the sender, indicating that the email cannot be delivered.

The "host" part of the message refers to the hostname or domain name of the email server that is supposed to receive the email. In other words, it's the name of the server that is supposed to handle the email delivery.

Common reasons for this error include:

To resolve this issue, you may need to: