Re: [exim] Accept Mail only to known recipients

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Author: Jeremy Harris
Date:  
To: exim-users
Subject: Re: [exim] Accept Mail only to known recipients
Odhiambo G. Washington wrote:
> I need some advise on a task I am working on towards spam control and
> bandwidth saving. I am going to have a dedicated server hosted somewhere
> upstream and this server is going to be my highest priority MX for several
> thousand domains.


I assume you have a low-bandwidth (or expensive) link?
Where are your secondary MX's (given that plenty of spammers hit them
by preference or stupidity)?

>
> Basically, I want to save as much bandwidth as possible by stopping spam
> and viruses upstream.
>
> There is not going to be any local deliveries on this server though.
> What I want to do is to "let it know" all the recipient addresses on
> the thousand domains. I'll be synchronising the list of recipients to
> this server at good intervals to keep the recipients list updated.
> Any mail that is not addressed to the "known" recipients need to be
> rejected out there, just like the identified spam and virii. I just
> need to get advise/warnings on:
>
> 1. What is the dandiest way to do this? After all dnsbl, I want to
>    accomplish all the checks at acl_smtp_rcpt and reject any unknown
>    recipients.


Do you have any constraints on data formats? That is, is your recipient
address list already in one place with you not wanting to do a
conversion? If it is, then you replication method needs to fit the
existing data store.

What is your allowable latency for an update - a few seconds, or days?

Do your secondary-MX systems need access to the same data?
With what update-latency?

Would merely having a database (pgsql, mysql or whatever) on the
primary-MX machine suffice, with you doing manual operations on it
using command-line tools from your downstream sites?

Cheers,
    Jeremy