Undeliverable and MX records

[paulha]

We are running exchange 2000 on 2000 server. A small percentage of emails to certain companies are returned as undeliverable.

They accept email from hotmail etc.

I have read the FAQ ref reverse lookup, our ISP assures us that reverse lookup is configured.

One thing that the companies that dont accept our mail have in common, is that when looking at the cached lookups in DNS, none of them have a MX record present. I assume that there is some relevance here, any ideas on how to proceed ?

Thanks in advance

 

[paulha]

sorry, that may be confusing. All emails to a small number of companies are returned undeliverable was what i meant to say

 

[brontosaurus]

cached DNS entries typically include only NS and

http://WWW records,

so don't worry about that...

if it's only a few companies, then it's probably not DNS, but you can't rule it out. i would triple check with your ISP to make sure that they've got all the entries correct and haven't changed any IP's lately...

also check if these companies are using blacklists, and make sure you're not on them...

 

[VOIPeng]

If your Mail server IP is on the Blacklist you won't be able to send to any Hotmail mail accounts so test by sending someone at hotmail an email and if you comes back check the following site to see if your server has been blacklisted:

http://mail-abuse.org/cgi-bin/lookup

or

http://spamcop.net/bl.shtml

Thank you,
Frank Mirecki

 

[paulha]

Thanks for the advice.

We can send and receive Hotmail etc. Nothing is listed at the mail-abuse/spamcop sites.

This is a potentially stupid question : Do I need an MX record on the DNS for the mail to get delivered ?

Thanks

 

[brontosaurus]

for delivery, no.

What nameserver is your exchange box using? What does the bounce message say on one of these failures? If you do an NSLOOKUP from the exchange box to one of these domains, can you get the MX?

 

[VOIPeng]

Yes you do need an MX record here is what is required on the DNS side of things:

How to Add DNS Records
After you configure the SMTP virtual server and the SMTP connector, you can send outgoing mail. However, incoming and return messages are not able to be delivered to you until you (or your ISP) configure DNS.
If your ISP is managing your DNS and you have a dial-up connection, the ISP must create a Mail Exchanger (MX) record that points to their smart host. This record uses the following format:
MX <your_domain>.com smart host1.<isp_domain>.com 10
MX <your_domain>.com smart host2.<isp_domain>.com 10

The preference value is 10, which can be used for preferential delivery or load balancing (as in this scenario). The ISP also have A (Address) records for smart host1 and smart host2.
If your ISP is managing your DNS records and you have a permanent link, the ISP adds the following record:
MX <your_domain>.com exchange.<your_domain>.com 10
MX <your_domain>.com smart host1.<isp_domain>.com 20
MX <your_domain>.com smart host2.<isp_domain>.com 20
A exchange.<your_domain>.com 131.107.2.200

If your link is down, your messages are delivered to the ISP's smart hosts and you can pick up your messages from the smart host. Also note that the A record must be explicitly entered.
If you are managing your own DNS records, add the following record:
MX <your_domain>.com exchange.<your_domain>.com 10
A exchange.<your_domain>.com 131.107.2.200

However, you may enter an MX record for a smart host as well.
If you have one or more SMTP front-end protocol servers, your DNS records look similar to the following record:
MX <your_domain>.com smtp1.<your_domain>.com 10
MX <your_domain>.com smtp2.<your_domain>.com 10
A smtp1.<your_domain>.com 131.107.2.201
A smtp2.<your_domain>.com 131.107.2.202

NOTE: If you are running your own DNS, your zone is mirrored on a secondary DNS server, possibly at another company location or with your ISP.

NOTE: It typically takes 24 hours for Internet DNS records to roll over.

Thank you,
Frank Mirecki

 

[brontosaurus]

I repeat - you DO NOT need an MX record to DELIVER mail.

 

[VOIPeng]

True brontosaurus, but it has to be set up to receive mail. You may want to look into your DNS Server settings for Exchange and ensure that they are set for reliable DNS servers, to set up DNS servers for Exchange go to:
Go into Exchange System Manager. Then under protocols for your Exchange server go into properties on the SMTP Virtual Server, and in the Delivery Tab click the Advanced button and click the configure button next to Configure External DNS Servers, here ensure that you have proper working DNS servers, should be your ISP DNS servers. Thank you,
Frank Mirecki

 

[View3D]

This could also be the Non-Deliverable sites are looking for a HELO response in SMTP. Although Hotmail is one of those sites and if mail is delivered to Hotmail thise may not be the case.......

What Non-Deliverable message are you getting?