[GLLUG] British Gas DKIM failure?

[Marco van Beek]

On 27/01/2024 18:08, Henrik Morsing via GLLUG wrote:
>
> I'm now getting the same from the Land Registry:
>
> I wish there was a test I could do to check what is actually wrong...
>
Okay, so this would indicate that it is more likely something wrong at 
your end rather than at theirs. I think that this point, I would start 
to wonder if there is anything at your end that is altering the email 
before it gets to the DKIM check.

So, I suggest you check good DKIM signatures against "bad" DKIM 
signatures, and look at which headers are being used to create the 
signature (the "h" in the DKIM header) and see if there is a patterns. 
On an email directly from me, you would see 
"h=Date:Cc:Subject:To:References:From:In-Reply-To:From;" in the header.

Maybe something in your system is altering something in a field that is 
being used by the British Gas and Land registry emails, like adding an 
"EXTERNAL" into the subject line before the DKIM test?

Regards

Marco