[kwlug-disc] Self-hosted email leaks home IP address

[Ron]

Chris Irwin via kwlug-disc wrote on 2026-03-10 13:37:

> On Tue, Mar 10, 2026 at 01:00:14PM -0700, Ron wrote:
>>
>> Anyone running Postfix to self-host email and notice that their home 
>> IP address is leaked in the first "Received: from" header?
> 
> Question: What is your mail setup?
> 
> I'm assuming:
> 
> 1. Self-hosted SMTP on "cloud" somewhere, with a public IP address

This is the setup, yes.


>     That SMTP server is public, it's IP is your domain's mx server, etc.
> 
> 2. You as a client, sending outbound via (presumably authenticated) SMTP
> 
>     Your public SMTP server does the "normal" thing of adding a    
> "received" header

Also correct.


> In this case, most hosted mail solutions don't do the "received" header 
> for authenticated outbound user mail. Gmail (as you tested) or fastmail 
> (which I tested), and presumably everything else.

Interesting. I suspect that hosting email for any medium sized org or 
larger has given this topic consideration and removes the first Received 
header. Which is good, IMHO.



>> I've got a temp work-around via header_checks:
> 
> Also, does this only act on mail you're sending? Or will mail you're 
> receiving be similarly altered?

All email - and every header of every email gets scanned.

It's suboptimal, I may implement a milter on submissions to change the 
first header instead.



> Why not an IGNORE rule to just drop that record entirely?

I did have a STRIP in the past, and it's just come up again so I thought 
I'd bring the topic up to see how others handle it.

I kinda like modifying the header, preserving some of the info like 
message ID. But it's a work in progress at the moment.


Stalwart email does not add that first Received header, interestingly 
enough...