Hi Dmytro,
On Sun, Jun 25, 2023 at 02:28:33PM +0100, Dmytro Homoniuk via mailop wrote:
> 450 4.3.2 Local problem - couldn't query foobar blacklist
>
> I do think this very hypothetical example is a bit of an outlier. It's
> providing non-actionable information to the sending system: it should read
> this and ... erm... reach out to you and tell you you may have your
> blacklist API malfunctioning?
I think that you are perhaps only considering this from the
perspective of a sender. When it comes to choosing text for SMTP
responses there are many different types of person involved and many
of them will not be thinking about "what will large senders think
about this text?" Even if maybe they should have.
Obviously you have the software developers of the mail servers
involved. Then you have the administrators of the systems who are
doing what they think is operationally best. Speaking as an
operator, I would previously have not hesitated to include some text
that I, my colleagues, my monitoring systems and any person watching
a port 25 conversation, might find valuable. Yes, it's often better
put in the logs and not sent out on the wire back to a client, but
that was previously not a strong concern for me and I think it's
also very likely not a big concern for many others making these
decisions.
So should we be putting out best practices documents for software
authors and systems administrators that say:
When considering responses:
- Only provide information that is actionable advice for the
client.
- Err on the side of being terse. Be more verbose in logs only.
I mean, that sort of advice seems reasonable anyway, but here we are
talking about it not just being reasonable, but in fact the
consequences may be, "or your user's mail may be silently deleted."
> As as sender I would be very satisfied with *"450 4.3.2 Local problem -
> retry later"* - this way you'd tell me the deferral is not exactly my
> fault, it's you and I'm not expected to figure out the issue on my own. And
> yes, if it persists - I'd be reaching out to ask about it, so if there is
> anything I can do - I would want it in the response.
Thing is, many of us thought we were operating in a world where the
text of a response was meant to explain what happened to anyone
interested, not SOLELY for telling senders what they need to do to
get this message delivered in future. What we considered we had at
our disposal for THAT was either 4xx or 5xx and that's it.
Isn't this an example of senders arguing that the SMTP response is
just for them, at the expense of everyone else who might have got
some use out of it?
The rest of your message tries to show an equivalence between
Michael deliberately temporarily rejecting an email (as opposed to
because of some unexpected problem) and SendGrid deciding to discard
it without any retries. I've mentioned before that I'm not really
interested in debating that one because my main concern here is the
unintended consequences of this practice.
Thanks,
Andy
--
https://bitfolk.com/ -- No-nonsense VPS hosting
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