sender verification

[David Woodhouse]

On Tue, 2004-02-24 at 14:59 +0000, Brian Candler wrote:
> Then you just discard it. (Exim's default is to freeze double-bounces; first
> thing you do on a new exim install is to get it to drop them silently. So
> much mail on our smarthosts was bounces to non-existent addresses..)

Site policy here is different. I like to _see_ frozen messages, and I
have freeze_tell set accordingly. Frozen messages occasionally alert me
to a _real_ problem.

Your site policy is fine by me. I have no objections; I prefer to
configure my system differently though.

> If you receive a (deliverable) mail, but refuse to accept it because you
> have determined that the return address is invalid, which is an accidental
> misconfiguration, then:
> - no mail will be delivered, and
> - no bounce will be delivered (at best you return 550 to the sending ISP's
>   smarthost, which is then left holding the baby and cannot do anything
>   with it)
> 
> I think think that's a worse situation than just delivering the mail in the
> first place.

Site policy here is different. I think it's better to reject early,
because if it stays on the _sender's_ queue, that's one hop closer to
the actual misconfiguration, and much more likely to get noticed by
someone who can actually fix it.

And from the converse POV, if I break something I'd _much_ rather have
my outgoing mail rejected at delivery time than accepted and
subsequently dropped.

But we really have digressed.

You won't convince me to stop, and I won't convince you to start -- and
I don't think either of us is actually _trying_ to achieve that :)

> Sure. But there are two halves to the equation:
> - implement signing of outgoing mails, and bounce validation
> - implement callback sender verification on incoming mails
> 
> If you implement either one or both of these, you gain immediate benefit. If
> the people you are communicating with implement them too, you gain even more
> benefit. And you don't have to wait for the rest of the Internet to
> implement them before you benefit.

Absolutely. 


-- 
dwmw2