How to Hide Exim Version in Email Message Sources?

1

Hey everyone,

I’ve been digging into my email server configuration lately, and I’ve noticed that the Exim version is visible in the headers of outgoing email messages. I’m concerned about this from a security perspective and I’d like to find out how to hide or obfuscate the Exim version to enhance the server’s security posture.

I’ve already checked and adjusted the smtp_banner and smtp_active_hostname settings in my Exim configuration, but the version information still seems to be leaking. I’m wondering if there are any additional steps or configurations I might have overlooked.

Is this where you hide versions?

smtp_banner = $smtp_active_hostname
smtp_active_hostname = ${lookup dnsdb{>: defer_never,ptr=$interface_address}{${listextract{1}{$value}}}{$primary_hostname}}

Has anyone here encountered a similar issue or successfully hidden the Exim version in outgoing email headers? If so, could you please share your insights or any tips on how to achieve this?

Thanks in advance for your help!

2

Hi @admin4system.com

Yes and I changed it too.

Edit /etc/exim4/exim4.conf.template and add below directive (you can add it at the top, after for example disable_ipv6 = true):

Note: replace Here the text you want to appear instead of Exim and the version by the text you want to appear in the received headers.

#Remove Exim version from received headers
received_header_text = Received: ${if def:sender_rcvhost {from $sender_rcvhost\n\t}{${if def:sender_ident {from ${quote_local_part:$sender_ident} }}${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}by $primary_hostname ${if def:received_protocol {with $received_protocol }}${if def:tls_in_ver        { ($tls_in_ver)}}${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}(Here the text you want to appear instead ox Exim and the version)\n\t${if def:sender_address {(envelope-from <$sender_address>)\n\t}}id $message_exim_id${if def:received_for {\n\tfor $received_for}}
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3

I added it and it didn’t change anything, you can still see:
Received: from localhost ([127.0.0.1] helo=) by hestia with esmtpa (Exim 4.95) (envelope-from <zapasowa@>) id 1rl6eU -00Ddji-91 for @gmail.com; Fri, 15 Mar 2024 13:27:10 +0100
I added this (test) + systemctl restart exim4:

received_header_text = Received: ${if def:sender_rcvhost {from $sender_rcvhost\n\t}{${if def:sender_ident {from ${quote_local_part:$sender_ident} }}${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}by $primary_hostname ${if def:received_protocol {with $received_protocol }}${if def:tls_in_ver{ ($tls_in_ver)}}${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}(Here the text you want to appear instead ox Exim and the version)\n\t${if def:sender_address {(envelope-from <$sender_address>)\n\t}}id $message_exim_id${if def:received_for {\n\tfor $received_for}}

4

Sorry, it works :slight_smile: I checked the wrong server.
Thanks a lot!

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