Re: Newbie to Exchange needs MX record info

CNAME records are discouraged from being used for mail handling.
A records and MX records are the preferred method.

Create an MX record for your domain, and whatever the A record is, it is.

As for the ISP's, each one will vary. There is no value in checking to see
if the sending host has an MX record as far as I'm concerned. SPF values
are worse then worthless IMHO as they allow a spammer to publish and then in
practice, many hosts would allow bypassing of normal checks.

Some ISP's do reverse lookup on the host to see if it belongs to the domain
that's sending. That's accomplished with a PTR record. You *should*
configure a PTR record for your sending host.

Can you post some of the NDR's you get for delivery if that doesn't clear
some of your issues up and the recipient domain ISP name?

Al

"Gary Demi" <GaryDemi@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:451DB892-823C-49EF-8569-A0C9CE761FA1@xxxxxxxxxxxxxxxx
> Thanks for the info.
> I already have an 'A' record, it consists of @ and my IP address this
> works
> fine for http, https and ftp access (with associated CNAME records)
>
> For Exchange Mail 2003 As I understand It,
> I create a 'Cname' record such as alias=mail , points to @ , ttl=3600
> then the MX record
> PRI=0, HOST=@
>
> This will allow other mail handlers to deliver mail to Exchange using
> anybody@xxxxxxxxxxxx (actual domain removed).)
>
> Wil this also fix the problem of bounced outgoing mail, as apparently many
> ISP's we send mail to apparently check to see if I am sending mail from a
> legit domain?
>
>
> Gary Demi
> Software & Communication Concepts, Inc.
> Microsoft Registered Partner
> Houston, & Phoenix
>
>
>
> "Al Mulnick" wrote:
>
>> The help file that comes with Exchange would be appropriate. Search SMTP
>> and
>> or Internet.
>>
>> MX records are not "required" per se to deliver mail per RFC. However, it
>> is
>> a best practice to have one that designates the mail handler for your
>> domain. This is accomplished by designating a host as a mail handler (MX
>> is
>> the designation for mail handler in DNS terms.)
>>
>> It is a best practice to designate a MX record that specifies a host by
>> it's
>> A record vs. any other type of record. During a SMTP transaction, the MTA
>> (mail transfer agent) will receive a message. It will determine where to
>> deliver that message and if it determines that message to be a remote
>> MTA,
>> it will then look at it's routing table to figure out if it knows how to
>> contact that responsible MTA. If it doesn't have a specific route, it
>> will
>> then look to DNS and specifically will look for a MX record that
>> specifies
>> the mail handler for that domain (domain here is everything to the right
>> of
>> "@" in the address.) If an MX record does not exist, the MTA will look
>> for
>> an A record. If that doesn't exist, it will fail the delivery and return
>> a
>> non-delivery receipt (NDR). If an MX record does exist, it should
>> reference
>> an A record. Once that A record is discovered, it will be queried for
>> it's
>> IP address and a conversation will be started between the MTA's via the
>> well
>> known SMTP port, TCP 25. Messages will then be transferred and the
>> recipient
>> MTA will become responsible for the next step of delivery.
>>
>> Basically, that's how it works. Daniel Petri seems to have taken the
>> time
>> to explain it as well.
>> http://www.petri.co.il/configure_mx_records_for_incoming_smtp_email_traffic.htm
>>
>> Having more than one MX record is done because the way SMTP mail works,
>> it
>> will try the lowest weighted (preferred) mail handler first. If it
>> receives
>> an error (depends on the error type), the sending MTA should then try to
>> send to the next mailer listed. This provides some level of failure
>> tolerance because you can have multiple hosts that receive mail for your
>> domain. Should one be out of service, the other should pick up the
>> slack.
>> It's not a requirement.
>>
>> Typically, your ISP will offer queuing services. If your host should be
>> down, they'll accept mail for your domain until you come back on-line at
>> which time they'll dump the queued messages to your mailer. So in
>> practice,
>> you'll often see records that look like:
>>
>> yourdomain.net MX preference = 10, mail exchanger = smtp.yourdomain.net
>> yourdomain.net MX preference = 50, mail exchanger = SMTP.yourISP.net
>>
>> Which would typically send mail destined for your domain to
>> smtp.yourdomain.net. However, if that server were unavailable, a sending
>> host would try to send the mail to the other server, SMTP.yourISP.net.
>> When
>> smtp.yourdomain.net came back into service, it would then receive the
>> queued
>> messages from the ISP MTA, SMTP.yourISP.net.
>>
>> One caveat to be aware of, is that some admins have configured their
>> hosts
>> to look for reverse DNS records as a way to reduce spam. I don't
>> consider
>> this effective, but that's my opinion. The reason I don't, is because I
>> can
>> have a sending host that is not also a receiving a host and therefore I
>> wouldn't have a corresponding MX record. To have the sending and
>> receiving
>> host be the same, is more often done in smaller IT shops vs. the larger
>> and
>> global shops. By RFC, I am not required to have an MX record for a host
>> that
>> is sending only nor would I want to as there would be no path for that
>> mail
>> handler to ever deliver a message. A PTR record is a good idea for your
>> sending host for the same reason. While not required, it is a good idea
>> to
>> more reliably transfer messages with your customers because some hosts
>> are
>> configured to check for a reverse lookup when receiving a message from
>> your
>> domain. Same goes with SPF records (you may want one); I don't spf
>> records
>> as effective nor desirable, but what do I know? ;)
>>
>>
>> Does that help?
>>
>> Al
>>
>>
>>
>> "Gary Demi" <GaryDemi@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>> news:1067F097-FA48-4B5F-97D3-5F0957549B12@xxxxxxxxxxxxxxxx
>> >I thought two MX records where required. The MX records should read
>> >something
>> > liklike mail.yourdomain.com or smtp.yourdomain.com (what prefix does
>> > Exchange
>> > use, and what help file are you referring to?
>> >
>> > Thanks
>> > --
>> > Gary Demi
>> > Software & Communication Concepts, Inc.
>> > Microsoft Registered Partner
>> > Houston, & Phoenix
>> >
>> >
>> >
>> > "Al Mulnick" wrote:
>> >
>> >> Two MX resource records?
>> >>
>> >> MX resource records are used to designate mail handlers for your
>> >> domain.
>> >> The A RR is the host name, and the MX references the A.
>> >>
>> >> If you have the A already, you would have your lowest priority MX
>> >> record
>> >> specify the A record as the mail handler. You may also want a reverse
>> >> PTR
>> >> (some domains check this record when receiving mail from you), but
>> >> that's
>> >> up
>> >> to you. The higher priority record, if you specify one, would
>> >> typically
>> >> be
>> >> for a backup mail handler such as might be provided by your ISP.
>> >>
>> >> Check out the help files for more information regarding MX and A
>> >> records
>> >> and
>> >> how to set this up. I believe it has mail flow pictures in there if
>> >> that's
>> >> helpful.
>> >>
>> >> Al
>> >>
>> >>
>> >> "Gary Demi" <GaryDemi@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>> >> news:9DEFC442-1929-4252-A261-BE4FFCA4A901@xxxxxxxxxxxxxxxx
>> >> > We are running SBS2003 premium and starting to use exchange. Right
>> >> > now
>> >> > we
>> >> > are
>> >> > running one NIC behind a NAT router.
>> >> >
>> >> > We have access to the DNS records on out nameserver through ouw
>> >> > domain
>> >> > registrar.
>> >> >
>> >> > We have a public domain name pointing to the SBS2003 computer (via
>> >> > the
>> >> > A
>> >> > record). To what URL do we point the two MX records (pri=0 &
>> >> > pri-10)
>> >> > so
>> >> > that
>> >> > Exchange Server is recognized as a mail server.
>> >> >
>> >> > A link to the the appropriate setup docs would be nice.
>> >> > --
>> >> > Gary Demi
>> >> > Software & Communication Concepts, Inc.
>> >> > Microsoft Registered Partner
>> >> > Houston, & Phoenix
>> >> >
>> >>
>> >>
>> >>
>>
>>
>>


.

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