Symptoms
Third-party tools that check for SMTP issues will report "Reverse DNS does not match SMTP Banner" for SMTP banner checks.
Description
By default, the Exim service will return the hostname in the SMTP Banner when receiving a valid helo. Some users may configure a different domain in the PTR record and receive this warning as a result of validation checks.
It is advised that the PTR record be updated to match the hostname to address this error. In some cases, this may not be desirable and the below workaround can be used to customize the SMTP Banner in Exim.
Procedure
Please note that only experienced system administrators perform the steps in this article. cPanel Technical Support does not provide assistance with the steps in this tutorial. These require customizations to the Exim service that will need to be manually maintained by the system administrator for your server.
- Log into WHM as the 'root' user.
- Navigate to "Home / Service Configuration / Exim Configuration Manager."
- Click the "Advances Editor" tab.
- Scroll down to the "smtp_banner" option.
- Change the "smtp_banner" value to the following.
"${smtp_active_hostname} ESMTP Exim ${version_number} \#${compile_number} ${tod_full} \nWe do not authorize the use of this system to transport unsolicited, \nand/or bulk e-mail."
- Scroll down to the "Section: BEGINACL" header.
- Click the "Add additional configuration setting" button above the "Section: BEGINACL" header.
- Select "smtp_active_hostname" from the dropdown in the line that was added.
- Add the following value for the "smtp_active_hostname" option.
"${if exists{/etc/custom_smtp_banner}{${lookup{$interface_address}lsearch{/etc/custom_smtp_banner}{$value}{$primary_hostname}}}{$primary_hostname}}"
- Scroll to the bottom of the page.
- Click the "Save" button.
- Access the server's command line as the 'root' user via SSH or "Terminal" in WHM.
- Run the following command.
touch /etc/custom_smtp_banner; chown root.mail /etc/custom_smtp_banner; chmod 640 /etc/custom_smtp_banner
- Open
/etc/custom_smtp_banner
in your preferred text editor. - Add entries using the
$IPaddress: $domain.tld
format for any IPs that use custom PTR records. For example:1.2.3.4: mail.domain.tld
Please note that the entries will not be automatically maintained and will require you to add or remove them manually as needed.
Comments
0 comments
Article is closed for comments.