On 23 August 2017 at 08:00, sreeranj s <sreeranj4dr...@gmail.com> wrote:
> Thanks Dominic. > > Let me explain what exactly is the issue. > Some of the external email server rejects email from our email servers > with 450 error. HELO name not resolvable in public DNS. To fix the issue I > have tried to change smtp_helo_name to match with mx, I have changed the > smtpd_banner also. However, when I telnet to our server over port 25, > banner is updated, but HELO still shows old hostname(internal name of > server). Is there any option to fix the issue. > > postconf -n shows the updated smtp_helo_name, but telnet still shows the > internal name. > > I haven't tried changing myhostname parameter, as there seems other > configuration parameters dependent on it I believe. More over we have a > passive mail server which always syncs configuration and mailboxes with > this active server(set up using keepalived). > > If I change myhostname, to external DNS name, could you please let me know > the other parameters that needs modification, like mydestination > I doubt the reason for the rejections by external mail servers is your helo name - this is not normally checked. In general it's not worth worrying about temporary rejections (4xx code), only about permanent ones (5xx code). A temporary rejection could be caused by greylisting, or the external mail server might have some temporary problem of its own. If your server has dynamic ip this is a (fatal) reason for rejection by many servers. Another could be that your ip or rDNS has been blacklisted. But in both cases I would expect to see a 5xx permanent rejection. I don't know if it is possible to set a non-standard 2nd smtpd response (after incoming 'helo') which seems to be '250 $myhostname', there is no smtpd_helo_name parameter to control this, but I don't think it relates to your problem. If you want to change myhostname parameter, look at http://www.postfix.org/postconf.5.html to check what else might change. Usually it's best to have myhostname the same as your rDNS (public reverse DNS name of your ip) - given for instance by dig +short -x [external_ip]. I set it explicitly in main.cf, and don't mess with smtpd_banner nor with smtp_helo_name.
