authentication server

[Juliano Silva]

How to solve this problem in proxmox mail gateway?

<admin@xxxxxx.com>: host mail.xxxx.com[107.xxx.xxx.xxx] said: 550-Please
turn on SMTP Authentication in your mail client.
550-(srv.proxmox) [204.xxxxxxxxxx]:41444 is not permitted to
relay 550 through this server without authentication. (in reply to RCPT TO command)

 

[mediaweb]

same problem here, any fix ?