Re: [exim] Feature I REALLY need - SMTP response strings

Heiko Schlittermann wrote:
> Hello,
>
> Marc Perkel <marc@???> (Fr 01 Dez 2006 18:18:19 CET):
>
>> I have one feature I really need. When verifying, in this case recipient
>> verify, I need to be able to read the string I get back from the target
>> server.
>>
>> I'm in the front end spam filtering business. Most of what I do is front
>> end filtering. The set their MX records to me, I fliter the spam, and
>> forward the good email to the original server. When people sign up I
>> read their current lowest MX and add it to a table that is used to
>> forward the mail to when I get done with it. Generally it works well.
>>
>
> Aha. But if the lowest MX is still at your customers, you'll miss a
> significant amount of the messages...
>

NO - all MX records point to my servers. I forward it to the original
server by using a forwarding table.
>
>> Here's the problem I'm trying to solve. The user changes their MX
>> records to my servers and at first everything works. Then 2 hours later
>> I get a call saying that email is being bounced. What happens is that in
>>
>
> The 2 hours might be because of DNS caching.
>

Yes - it is because of DNS caching. That's the problem. It lets me think
it's working and then the caching wears off and it starts rejecting
email. What I need to do is to be able to detect that and become aware
of it earlier that I now do.

>
>> some cases the original server thinks it is no longer the server for
>> that domain because it is no longer the lowest MX record so it replies
>> that my server is not authorized to relay through their server.
>>
>
> The customers server should be configured to have its local domains
> "hard wired", not just relying on DNS answers.
>

Many customers have no idea how they are configured because they are
buying service from a vendor that takes care of that.
>
>> What I need to do is detect that this is happening and at least store
>> the incoming email and alert me that there's a problem. I have yet to
>> find a solution. But if I could do a callout and look at the response to
>> see if the word RELAY is in it then that would be a very good indication
>> that the target server is misconfigured.
>>
>
> $acl_verify_message ?
>

Nope - that doesn't do it. The docs would leave you to think it is but
it's just a Exim generated code.