Author: Ian Eiloart Date: To: Renaud Allard, Craig Whitmore CC: exim-users, Artem S. Tashkinov Subject: Re: [exim] Ultimate spam defense - check for the sender MX record
--On 27 December 2006 10:25:20 +0100 Renaud Allard <renaud@???>
wrote:
>
>
> Craig Whitmore wrote:
>>>> I would like to increase a spam defense of our server by checking if a
>>>> sender really represents an MX server of his/her organization. So if a
>>>> certain PC is trying to send me an e-mail from user@??? then we
>>>> will check if this person's IP address is within MX servers of
>>>> domain.com, otherwise we'll refuse to accept the mail.
>>>>
>>>> Is it feasible? How can I achieve this?
>>>>
>>
>> If a domain has set up SPF or SenderID records then you can use those so
>> make sure the emails are coming from the correct places.
>>
>
>
> Unfortunately, many sites who have implemented SPF have implemented them
> incorrectly.
> Here is a very good example:
> /var/log/exim4/rejectlog.13.gz:2006-12-14 15:51:53 H=host60.citrix.com
> (FTLPEXCHSMTP01.citrite.net) [66.165.176.60]
> F=<citrix_license@???> rejected RCPT <sorryfor@obfuscation>: SPF
> check failed.
>
> If you strictly check SPF, you will reject good mails because many sites
> administrators just forget they have servers sending mails from web
> interfaces or in an automated way.
Rejecting their emails should be an efficient way of concentrating their
minds on fixing the problem.
