Re: MX Record Question

Phillip Windell

In talking to our ISP the guy's comment about SPF records was "hardly anyone
uses them", but I think that is going to change.
In any case, I think the SPF records are going to be the way of the future
in the battle with SPAM. They just seem to me to be the logical next step
for the industry to take.


--
Phillip Windell


The views expressed, are my own and not those of my employer, or Microsoft,
or anyone else associated with me, including my cats.
-----------------------------------------------------

"Kevin D. Goodknecht Sr. [MVP]" <.US> wrote in message
news:.gbl...
> Read inline please.
>
> In news:%.gbl,
> Phillip Windell <> wrote:
>> "Bryan" <> wrote in message
>> news:...
>>> I was looking at microsofts SPF Record Wizard and they ask a
>>> question about Inbound Mail Servers Send Outbound Mail....they want
>>> you to check each MX address to make sure it is a valid outbound
>>> e-mail server for the domain that
>>> is why I was asking.
>>
>> It has to do with the IP# that outbound mail shows as comming from. The
>> SPF record purpose is to list the IP#s that are authorized to be
>> "senders" or mail for your particular domain (even if they aren't
>> related to any MX record).
>
> This is not entirely correct, while the SPF may list the valid IPs for
> outbound mail servers, another way to do it, that is just as valid,
> providing the inbound SMTP is also (or only) the outbound SMTP you add mx
> to the SPF.
> For example.
>
> domain.com TXT v=spf1 mx -all
>
> This SPF states that ONLY MX servers for domain.com can send mail from
> domain.com the "-all" means that if any other server tries to send mail
> from domain.com, it is considered a hard fail and should be rejected.
> One problem that can arise from this is, if your MX records are not
> properly created with the SMTP HELO greeting, your mail may be rejected.
> In addition, the PTR should name the SMTP HELO greeting, too.
>
>>
>> For example our MX record does not even point to the IP# for our mail
>> server at all,...it points to the IP# of our SPAM Filtering
>> System,..but outbound mail from us does not go through the SPAM
>> Filtering System but comes from the mail Server itself which is
>> associated with a different Public IP# that has nothing to do with
>> our MX record so mail from us does *not* come from the IP# of any of
>> our MX Records. So if you "test" our mail's IP# it will not
>> correspond to the MX Records. So if I am not mistaken the SPF record
>> will list these "other" IP# and it is basically saying "Yes it is OK
>> for these numbers to be senders for this domain."
>
> While your SPF may be something like this:
>
> domain.com TXT v=spf1 ip4:IPADDRESS -all
>
> This is just as valid:
>
> domain.com TXT v=spf1 a:smtp.domain.com -all
>
> Either way you need both need an A record for the outbound SMTP HELO name
> and a matching PTR record, because PTR records are required to have a
> matching A records.
>
>
>
> --
> Best regards,
> Kevin D. Goodknecht Sr. [MVP]
> Hope This Helps
>
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