blog.plee.me About software, technology and random things

16Nov/142

Mozilla Thunderbird: Changing the EHLO / HELO Value in the “Received”-Header for Outgoing Mail

Hi!

If you have had a look at your outgoing e-mail headers that you've sent from Mozilla Thunderbird, you might have noticed that Thunderbird uses the IP of the network interface that it uses to connect to the internet with by default. If you are using a router on your network, this is a private IP from your LAN (for example 192.168.1.2) instead of one that might be of actual use.

Example:

Received: from external.sender.host.example.org ([123.123.123.123] helo=[192.168.1.2]) by
 mail.example2.org (incoming-mta-service) with esmtpsa (outgoing-mta-service) id
 0a1b2c-3D4e5F6G7h-0a1B2c for <[email protected]>; Sun, 02 Nov 2014 20:55:41 +0100

where "123.123.123.123" is the publicly facing IP and "external.sender.host.example.org" is its hostname.

If you do not wish to expose this information to every and all recipients of the e-mails you are sending with Thunderbird to (maybe out of security concerns in a business environment), you can set the EHLO / HELO value manually for every outgoing e-mail sent by the Thunderbird client with your current user profile and even for every simple SMTP server individually.

Here's how:

Globally

  • Open your Thunderbird options ("Tools" => "Options")
  • "Advanced" => "Config Editor..."
  • Create (or edit) the entry named "mail.smtpserver.default.hello_argument". If you need to create it, use right-click => "New" => "String".
  • Change the value to the desired IP or hostname (FQDN).

Per SMTP server

  • Open your Thunderbird options ("Tools" => "Options")
  • "Advanced" => "Config Editor..."
  • Create (or edit) the entry named "mail.smtpserver.smtp<number>.hello_argument" where <number> is the ID for the SMTP server you would like to apply the setting to. Type "mail.smtpserver.smtp" to see which ones are available and which ID they have. If you need to create the entry, use right-click => "New" => "String".
  • Change the value to the desired IP or hostname (FQDN).

Technically this value is not relevant for sending/receiving the mail, but because it might be used for spam scoring or simply out of courtesy I would recommend entering a valid IP / hostname.

I myself am using 127.0.0.1.

Thanks for reading!

Sources:

   
%d bloggers like this: