Re: [Exim] Blocking sobig.f

>To: nico@???
>From: Tony Finch <dot@???>
>Cc: exim-users@???
>Subject: Re: [Exim] Blocking sobig.f
>Date: Wed, 20 Aug 2003 17:07:38 +0100
>
>Nico De Ranter <nico@???> wrote:
>>
>>How would you check whether a mail address exists?
>
>callouts.

Use callouts with caution. They can be expensive on a busy machine.
And *aren't* guaranteed to give a definitive answer. See Section
37.5 of the manual. In particular the description of the "random"
option.

As a specific example, we relay mail for several domains. We have
no idea what their email aliases are, so will happily relay email
for:

{any-old-address}@{relay-domain}

I regularly see incoming email for defunct/guessed email addresses
at our relay domains. And can't return the resulting error message
because the sending spammer forged the envelope sender. However
that's my cross, I'll just have to bear it :-( A decent malt whisky
helps :-)