smtp_helo_name not changing.

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smtp_helo_name not changing.

sreeranj s
Hi,

I am trying to change smtp_helo_name in our email server(postfix 2.6.6) to match with the one in mx record. 

I have specified the value as the one given below in main.cf, and reloaded the postfix. However telnet still shows the hostname as helo name. I could change the smtp_banner, but not smtp_helo_name.

smtp_helo_name = mx.mydomain.com


Any help on achieving this would be highly appreciated.
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Re: smtp_helo_name not changing.

Dominic Raferd
On 23 August 2017 at 07:11, sreeranj s <[hidden email]> wrote:
I am trying to change smtp_helo_name in our email server(postfix 2.6.6) to match with the one in mx record. 

I have specified the value as the one given below in main.cf, and reloaded the postfix. However telnet still shows the hostname as helo name. I could change the smtp_banner, but not smtp_helo_name.

smtp_helo_name = mx.mydomain.com

​smtp_helo_name is used for outgoing connections i.e. when postfix sends email (smtp != smtpd).
smtpd_banner is for how postfix responds to an incoming connection.​

Why not:
myhostname​ = mx.mydomain.com
This is used by default in both smtp_helo_name and smtpd_banner.

​BTW, postfix 2.6.6 is seriously old...​
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Re: smtp_helo_name not changing.

Dominic Raferd


On 23 August 2017 at 08:00, sreeranj s <[hidden email]> 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.