Hello, I`m experiencing some untypical issue and i was not able to find solution here so i`m opening new Thread . One of my clients is trying to setup forwarding for one of his mail account but when the message is send to the mail account on the domain hosted on my server it is not forwarded but it`s rejected with the following message: This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: firstname.lastname@example.org SMTP error from remote mail server after RCPT TO:<email@example.com>: host mx10.mailspamprotection.com [18.104.22.168]: 550 relay not permitted! ------ This is a copy of the message, including all the headers. ------ I have try to forward to 3 different mails ( yahoo, gmail and some from our own servers ) but getting the same message. Any suggestion? The domain having the issue is located in /etc/localdomains .