Fixing DMARC & Reverse DNS does not match SMTP Banner

mytpanel

Registered
Nov 4, 2017
1
0
0
United States
cPanel Access Level
Reseller Owner
Hi everyone!

So I've learned a ton about SPF and other sending authorizations, but using mxtoolbox, I still have the following issues. The site is - Removed -

Code:
1 Error(s)
Category Host Result
[IMG] dmarc example.com DNS Record not found
7 Warning(s)
Category Host Result
dns example.com SOA Serial Number Format is Invalid
 dns example.com SOA Expire Value out of recommended range
smtp gmr-smtp-in.l.google.com Reverse DNS does not match SMTP Banner
smtp alt1.gmr-smtp-in.l.google.com Reverse DNS does not match SMTP Banner
smtp alt2.gmr-smtp-in.l.google.com Reverse DNS does not match SMTP Banner
smtp alt3.gmr-smtp-in.l.google.com Reverse DNS does not match SMTP Banner
smtp alt4.gmr-smtp-in.l.google.com Reverse DNS does not match SMTP Banner
I've read on some threads that these "don't matter". That said, I'd like to still understand how to fix them.

* I'm using Google DNS.
* I'm using a third party mail relay, which is good for the SPF, everything works properly.
* I have inbound emails forwarded directly through Google Domains to another email inbox.

From what I understand:
* The SOA warnings are built into the DNS server, and I likely do not have access to them unless I'm hosting my own DNS through cpanel.

But what do I do to fix the dmarc & Reverse DNS?
 
Last edited by a moderator:

cPanelMichael

Administrator
Staff member
Apr 11, 2011
47,884
2,254
463
Hello,

If the email and DNS is hosted on the cPanel server, you can setup the DMARC record using the "Add DMARC Record" instructions from the following document:

Zone Editor - Documentation - cPanel Documentation

The reverse DNS warnings appear to stem from Google. You won't be able to alter those records because they are controlled by Google as opposed to your cPanel server.

Thank you.
 

amccristovao

Registered
Jul 15, 2020
1
0
1
Angola
cPanel Access Level
Root Administrator
Hello,

For the Reverse DNS does not match SMTP banner i got a solution it worked for me:

at the top of exim.conf (line 2):

disable_ipv6
local_interfaces = 127.0.0.1 : aaa.aaa.aaa.aaa : bbb.bbb.bbb.bbb : ccc.ccc.ccc.ccc
smtp_active_hostname = ${lookup{$interface_address}lsearch{/etc/virtual/smtp_active_hostnames}{$value}}
smtp_banner = "$smtp_active_hostname ESMTP $tod_full"

exim.conf driver section (line 2015)

remote_smtp:
driver = smtp
headers_rewrite = * ${perl{get_headers_rewrite}} f
headers_add = "${perl{get_headers_rewritten_notice}}"
interface = "${lookup{$sender_address_domain}lsearch{/etc/virtual/domainips}{$value}{aaa.aaa.aaa.aaa}{bbb.bbb.bbb.bbb}{ccc.ccc.ccc.ccc}}"
helo_data = "${lookup{$sending_ip_address}lsearch{/etc/virtual/helo_data}{$value}{$primary_hostname}}"
hosts_try_chunking = 198.51.100.1


create directory /etc/virtual/

Inside this directory create this 3 files:

"smtp_active_hostnames" with following content:

aaa.aaa.aaa.aaa: mail.hostname_for_domain_a
bbb.bbb.bbb.bbb: mail.hostname_for_domain_b
ccc.ccc.ccc.ccc: mail.hostname_for_domain_c

"helo_data" with following content:

aaa.aaa.aaa.aaa: mail.domain2.com
bbb.bbb.bbb.bbb: mail.domain3.com
ccc.ccc.ccc.ccc: mail.domain4.com

"domainips" with following content:

domain_a: aaa.aaa.aaa.aaa
domain_b: bbb.bbb.bbb.bbb
domain_c: ccc.ccc.ccc.ccc

Hope it helps