roundcube does not send or receive emails

[shoeder]

I have a problem with the mail server, since it does not receive e-mails from outsiders, and neither does it send e-mails to the denitarians, it appears as if it had already sent them, but there is really nothing in the receiving mail.

Could not deliver to these recipients or groups:
[email protected] ([email protected])
The message was not delivered. Despite repeated attempts to deliver the message the recipient's email system has refused to accept a connection from the email system.
Contact the recipient by some other means (by phone, for example) and ask them to tell your email administrator that their email system appears to be rejecting connections from the email server. Please provide the error details shown below. Only the recipient's Email Manager can fix this problem.
For email administrators
No connection could be established because the target computer has actively denied the connection. This typically occurs when trying to connect to a service that is idle on the remote host, that is, no application is running on the server. For more information and tips to fix this problem, see this article: https://go.microsoft.com/fwlink/?LinkId=389361