Exchange not cycling through multiple MX records

[MoobyCow]

Here's the problem, we're trying to send email to a company that has multiple MX records like so:
xxx.com. MX IN 43200 smtp.xxx.com. [Preference = 20]

xxx.com. MX IN 43200 mail1.xxx.com. [Preference = 10]

The server mail1.xxx.com is not active (I can not telnet to it, it rejects SMTP connections)

The second server (smtp.xxx.com) accepts connections.

On our Exchange server the mail is caught in the SMTP queue and will not go out. I think it is because it never tries the lower preference server (smtp.abac.com)

Any thoughts on why Exchange would not cycle to the secondary MX record when it fails with the first one?

 

[MoobyCow]

I was able to fix this by putting the MX record in DNS. I hope this in not my only option though and I'd still like to hear if anyone has some thoughts on the problem.

 

[MoobyCow]

I just wanted to bring this to the top as it happened to me again and I still have no good solution outside of hardcoding the MX record in DNS.

 

[doomwar]

Hi Mooby,
I appear to have exactly the same problem, I have spent the last few days, occaisionally pulling out low pref MX records from my DNS server. :-(
Microsoft say Exchange does cycle thru MX records, yeh, right. But notes problems if an external DNS server is used, so I promptly made sure the EX2K server had some forwarders and removed the external dns refs from the SMTP servers. No joy :-(
But I am now wondering if it has anything to do with my security setup, the Ex2k server posts out to an smtp proxy, inside my firewall and I am wondering if it is/is not giving the Ex2k server the same responses that a failing SMTP server would. i.e. the Ex2k server doesnt understand that the first MX server is actually unavailable.
Make any sense?

 

[glippi]

I've reviewed the problem and think i have found a sollution:

An MX record has three parts: your domain name, the name of the machine that will accept mail for the domain, and a preference value. The preference value lets you build some fault tolerance into your mail setup.

Your domain can have multiple MX records, such as the following:

Acme.com mail.acme.com 0; Acme.com mail2.acme.com 10; and Acme.com mail.isp.net 100.

In this case, mail delivery will be attempted to mail.acme.com first because it has the lowest preference value. If delivery fails, mail2.acme.com will be tried next. If mail2 is also down, mail will be sent to a relay host called mail.isp.net, which in this case is at Acme's ISP.

If you plan to use your ISP's DNS server, you'll also need to have the ISP set up some A records, which associate IP addresses with computer names. Each of the computers mentioned in your MX records needs an A record to associate them with an IP address.

===========================================================
I have copied this from an article, please check these things first, becausse i have experience that exchange does cycle thru the MX records

Full article on DNS records :

http://www.netline.be/formations/cours/dns/

With Love & Grtz,

Glippi

** Intellectuals solve problems; geniuses prevent them. **

 

[MoobyCow]

I really don't know what the problem is, because it works for some domains with multiple MX records. I think Ex2k knows that the server is unavailble, it has to queue the message after all. But I could be wrong. I think your setup is common enough that it shouldn't cause a problem.

I upgraded to 2003 over the weekend (for reasons unrelated to this problem), hopefully that will fix the problem.