Hide information sent by Exim4

Tom

4/30/24, 6:21 PM

I am working with RabbitMQ + PHP to receive send email requests from my application. When RabbitMQ receives the request, PHP uses PHPMailer to connect to the Exim server and send the email.

However, I saw the original message and noticed that the IP of the PHP machine that made the request to Exim (so far OK), the name of the VM that the PHP VM (that's not OK), and the server's Exim version (Definitely not OK).

Received: from <GOOGLE-PUBLIC-IP>.bc.googleusercontent.com 
([MY-VM-PUBLIC-IP] helo=MY-RABBITMQ-PHP-VM-NAME) 
by my-exim-server.example.com with esmtp (Exim 4.90_1) 
(envelope-from <[email protected]>)

How can I hide the PHP VM name and Exim version (even the Exim name) in the email that is sent to the client?

2 + 0

exim

Score:1

Server

vidarlo

4/30/24, 7:56 PM

As default, hostname is used for helo field. You can change that using the primary_hostname directive.

For version, that's the smtp_banner option.

If any of those is problematic for security reasons, you should probably revise your security practices.

+ 0

Score:1

Server

Jasen

5/1/24, 10:38 AM

To change the received header, Edit (or set) the received_header_text setting of the exim server instance.

But first consider why you want to hide this information.

If the server has an embarrassing or controversial name, rename it before it leaks out some other way... If any of the other information is a security risk you have already lost.

When you hit email delivery problems, or the server suddenly starts emitting batches of 100000 emails. having that information will be very useful.

+ 0

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Hide information sent by Exim4

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.