Re: [exim] Help with dropping spam e-mail.

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Author: Yves
Date:  
To: mje, exim-users
Subject: Re: [exim] Help with dropping spam e-mail.
On Tue, 15 May 2018, Mark Elkins via Exim-users wrote:
> On 14/05/2018 12:25, Jasen Betts via Exim-users wrote:
>> On 2018-05-14, Mark Elkins via Exim-users <exim-users@???> wrote:
>>> Someone is using "please@???" as the source of spam e-mail. The
>>> address does not exist...
>> step 0: publish an SPF record.
> except there is no guarantee that I am the only method of sending
> e-mail's out for this domain. I do run mail submission relay services
> for those that ask. Many customers still use their Internet service
> provider though to send out email

SPF records are managed by the domain name owners because you need to be
able to publish to the domain's DNS.

If a client of yours sends emails through their own servers, _and_ through
yours, then it is up to them to configure their own SPF records, listing
their own servers, and _including_ your domain's SPF rules.
Indeed, I suppose that in this case, the domain name being used is that of
the client; I cannot imagine that you let your clients send emails through
servers of their own choosing using _your_ domain name...
I did such a thing in my limited case: I have my own server, but I send
emails through my ISP's smarthost, thus my SPF records lists my server (by
name), and includes my ISP's SPF rules.

For your clients that use only your servers to send emails, then in theory
it would depend on who has authority on the domain. However, in such
cases (for example mail from companies that get handled by Microsoft), the
management of the DNS may be actually handled by the mail operator (you).
So you would publish the SPF records listing your servers, on behalf of
these clients.

>>> ...but I do manage the domain "help.co.za"
>>> or - somehow tell exim when it gets an unknown user to /dev/null it ???
>> can you instead tell exim which are valid users?
>
> The problem only arises for domains that I host. Need to sit down next
> to Lena (or a similar person) and have them check my configuration.
> (Is Lena at RIPE? - got friends there)
>
> -- 
> Mark James ELKINS  -  Posix Systems - (South) Africa
> mje@???       Tel: +27.128070590  Cell: +27.826010496
> For fast, reliable, low cost Internet in ZA: https://ftth.posix.co.za


Cheers,
Yves.