Re: [exim] mx records

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Author: Oliver von Bueren
Date:  
To: exim-users
Subject: Re: [exim] mx records
Hi Mostafa

I don't suggest you use such a test as it is not unusual that the
sending mail server is a different one than the receiving mail server
for a given domain altogethers. This means, that you won't find the IP
of the connected server in any of the MX records, which is perfectly legal.

To make it more complicated, the MX record of which domain do you like
to get? If the connecting server identifies itself as
mailout.domain.com, getting an MX for that could very well fail. Getting
the MX record of domain.com might give you mailin.domain.com on another
IP, which is no problem at all. To make it worse, the server could
identify itself correctly as mailout.state.country.domain.com. Which
part of that name would you use to get an MX from?

If you like to check the helo name I suggest you take the example
configuration of Exim and use those bits that check the characters used
in it as well as some simple checks to make sure the name given is not
your own IP address or host name.
And those checks I've got in my RCPT-ACL, as I don't reject HELO,
doesn't give you anything, the remote host will just retry.

BTW: And don't do any helo checks on your submission port (the one your
users use to send out (aka relay) mail), MUAs are far from perfect!

       Oliver





Mostafa Fouad wrote:
> Dear Sir
>
> i have exim 4.68
>
> and i want to know how can i check the following
> check the connetced ip address to be ONE or MORE of the mx record of the sender_helo_name and that in the acl_check_helo access list
>
>
>
> or there's already in exim built-in function i just enable it
>
> thanks
> mostafa
>
>
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