SMTP HELO can not be changed / specified

BearTM · September 30, 2022, 5:30pm

NethServer Version: 7.9.2009
Module: Postfix

I’ve tried to set the SMTP HELO message to my domain, but none of the settings appear to be working when being checked by MX Toolbox:

Reverse DNS from IP Address returns:

mail.domain.net

Checked in Cockpit Relay settings:

Custom HELO: mail.domain.net

Checked in console Configuration:

postfix=service
HeloHost=mail.domain.net

Checked in /etc/postfix/main.cf

smtp_helo_name = mail.domain.net

Checking with MXToolbox
Transcript : 220 domain.mail.local ESMTP Postfix [137 ms]
Transcript : EHLO keeper-us-east-1d.mxtoolbox.com
Transcript : 250-domain.mail.local

Which fails the MX Toolbox HELO match check.
There are NO custom templates for /etc/postfix/…

Does anyone have any ideas why the HELO setting (confirmed correct) in main.cf is not being applied in the Postfix HELO response?

Andy_Wismer · September 30, 2022, 6:06pm

@BearTM

Hi Rob

And welcome to the Nethserver community!

Additionally, this seems to be needed in /etc/postfix/main.cf:
myhostname = example.com

I have this in my notes:

————————————————————
Postfix
————————————————————

Custom Template addition for Postfix:

mkdir -p /etc/e-smith/templates-custom/etc/postfix/main.cf

cp /etc/e-smith/templates/etc/postfix/main.cf/40helo /etc/e-smith/templates-custom/etc/postfix/main.cf/40helo

nano /etc/e-smith/templates-custom/etc/postfix/main.cf/40host

Add in:
myhostname = example.com

Save with CTRL-x y ENTER

expand-template /etc/postfix/main.cf

signal-event nethserver-mail-server-update

systemctl restart postfix
systemctl status postfix

Hope this helps…

My 2 cents
Andy

davidep · September 30, 2022, 6:28pm

Hi Rob!

Some good guy added the custom helo setting to the Cockpit UI at some point, according to the manual page

https://docs.nethserver.org/en/v7/mail.html#custom-helo

IIUC it’s under Email > Relay

To Andy: update your notes!

BearTM · September 30, 2022, 6:42pm

@davidep … well, the issue is that I’ve already followed that guide, and set the Email > Relay > HELO Host … verified that in the console db postfix settings, checked the generated postfix/main.cf file, and verified the reverse DNS. It’s all correct!

@Andy_Wismer , I’ll try adding in a custom template for “myhostname”, but the explicit override in postfix/main.cf should be taking care of that already … will update shortly.

Andy_Wismer · September 30, 2022, 6:44pm

@davidep

Salutti Davide
Hello Rob

I did use the custom-helo, but wasn’t enough in my case.
This sets the helohost directive in in /etc/postfix/main.cf (using template
/etc/e-smith/templates/etc/postfix/main.cf/40helo)
But as said, it didn’t suffice the mail tests.

Adding the myhostname directive helped.
So actually, i’m using both directives and it works now…

My 2 cents
Andy

Andy_Wismer · September 30, 2022, 6:51pm

I fully agree, and I did report in the forum that it wasn’t enough (or not the right directive?), but it seemed to work for some users here.

It did not work for my mail tests.

Not all mail tests were created equal, some are really good, others are a waste of time…

To manually verify, use a simple telnet (Or PuTTY in telnet mode)

telnet yourmailserver.domain.tld 25

You should see the helo displayed…

My 2 cents
Andy

BearTM · September 30, 2022, 7:01pm

@Andy_Wismer - Sweet! The addition of the custom template solved it.

As you said, I needed to create the file:
/etc/e-smith/templates-custom/etc/postfix/main.cf/40hostname

but instead of hard-coding in the domain name, I instead added in:
{ $postfix{'HeloHost'} ? "" : "# " }myhostname = { $postfix{'HeloHost'} }

Then:
expand-template /etc/postfix/main.cf

And checked the main.cf contents (to be absolutely sure):
smtp_helo_name = mail.domain.net
myhostname = mail.domain.net

Restart the mail server:
signal-event nethserver-mail-server-update

And everything is now working 100% from MX Toolbox:
Transcript : 220 mail.domain.net ESMTP Postfix [111 ms]
Transcript : EHLO keeper-us-east-1d.mxtoolbox.com
Transcript : 250-mail.domain.net

Thank you!

I think we need to update the generation templates (in the future) to handle this correctly:

/etc/e-smith/templates/etc/postfix/main.cf/40helo

#
# 40helo -- Customizable SMTP HELO value #2767
#
{ $postfix{'HeloHost'} ? "" : "# " }smtp_helo_name = { $postfix{'HeloHost'} }
{ $postfix{'HeloHost'} ? "" : "# " }myhostname = { $postfix{'HeloHost'} }

So that this will work “out of the box” for everyone.

Andy_Wismer · September 30, 2022, 7:03pm

@BearTM

See this:

Helps the next dude…

My 2 cents
Andy

I also use mxtoolbox.com (among others…), mail-tester.com is another good one

BearTM · September 30, 2022, 7:11pm

@Andy_Wismer

I gave mail-tester.com a go, and received a “Wow! Perfect, you can send 10/10 score”, with it warning only that I didn’t send a “List-Unsubscribe header”.

Thanks for your quick and comprehensive answer!

Andy_Wismer · September 30, 2022, 7:12pm

And thanks for that!

We are proud of our little forum here…

mail-tester.com is focused on Spam (For mass mailers?).
But works quite well and comprenhesive.

Andy_Wismer · September 30, 2022, 7:17pm

I’d suggest adding the templates as suggested, right from the dev side.
You’re the dev!
Me? My job is to connect hosts and make sure they communicate as needed…

BearTM · September 30, 2022, 7:21pm

Yes - I edited my earlier comment to the following:

Create the custom template file:
/etc/e-smith/templates-custom/etc/postfix/main.cf/40hostname

but instead of hard-coding in the domain name, I instead added in:
{ $postfix{'HeloHost'} ? "" : "# " }myhostname = { $postfix{'HeloHost'} }

Then:
expand-template /etc/postfix/main.cf

Restart the mail server:
signal-event nethserver-mail-server-update

And everything is now working 100%.

davidep · September 30, 2022, 8:18pm

OMG …I’m sorry guys! I completely missed the point

https://www.postfix.org/postconf.5.html#myhostname

The default is helo = hostname, not the contrary.

The proposed change would alter the semantics of the existing setting: I tend to disagree with it.

Andy_Wismer · September 30, 2022, 8:46pm

@davidep

Further down you can see:

smtp_helo_name (default: $myhostname)

What we’re using is actually NOT the correct way, as it seems.
Default - per Postfix - is actually myhostname…

However: this is somewhat stupid, as it violates RFCs about the requirement to use “A” records, NOT CNAMEs for DNS Mail server records.
MX entries are neither CNAME nor A records.
But an MX needs to point to something resolveable (wiith DNS).

smtp_cname_overrides_servername (default: version dependent)
When the remote SMTP servername is a DNS CNAME,

It also results in a (nowadays) hardly usable mail smtp server…

My 2 cents
Andy

davidep · October 3, 2022, 11:40am

Yes IIUC it is not fully consitent with RFCs.

Good news are that for NS8 the Mail module allows to set $myhostname to a free host FQDN value: there shouldn’t be the need of the custom HELO any longer.