We have an Ubuntu server install with sendmail, apache and php running.
The server is internal to our network and is not accessible outside of our network.
The intranet sends emails to clients and does this usually without issue however for one client I am receiving a bounceback as follows:
"The message reached the recipient's e-mail system, but delivery was refused. Attempt to resend the message. If it still fails, contact your system administrator.
< intranet.mycompany.local #5.2.1 SMTP; 550 5.2.1 Mailbox unavailable. No reverse name (PTR) for your sender IP ()"
I'm not sure exactly where the issue lies, is it because it cannot resolve intranet.mycompany.local to the IP in brackets or is it that the IP in brackets does not resolve to an address?
Any help with this would be greatly appreciated. If you need anymore information please don't hesitate to ask.