Have you ever seen Exchange choose the wrong MX record?

[fakesoundofprogress]

Hi all,

Something I am curious about. Another organization has been unable to send email to our domain. They are the only domain who seems to have this problem. We can receive mail from what seems like every other domain out there

Anyway, turns out their Exchange 2007 server was unable to establish a connection to our mail server. I suspect because it was using the wrong MX record or possibly the A record for the domain.

I had 4 MX records listed. One was our primary mail server 3 were for backups (provided by another company). They looked something like

MX 0 email.mydomain.com
MX 20 backup.othercompany.com
MX 20 backup2.othercompany.com
MX 20 backup3.othercompany.com

Now, recently we canceled our service with Othercompany.com, but had not updated our DNS records.

After learning of this domain that could not send to us, I cleared the other MX records and just left the record for our main email server. Then things started working again.

Now I should mention that during this time, our primary email server never went down. So, I am wondering why would these invalid MX records cause a problem for this other domain? Should Exchange not always try to deliver to email.mydomain.com since it has preference 0?

Google search revealed some others who claim the same thing. Anyone else ever see this and know why something like this would happen?

 

[58sniper]

Just because your primary server never went down doesn't mean the path between their server and your server wasn't interrupted. At which point, Exchange would roll over to the next MX record.

Pat Richard MVP
Plan for performance, and capacity takes care of itself. Plan for capacity, and suffer poor performance.

http://www.ucblogs.net/blogs/exchange/

 

[fakesoundofprogress]

True, but should Exchange not try the MX record for the primary server the next time it tries to send to us? In this case it never seemed to, even after the backup servers didn't respond. This spanned a couple of days, so I don't think it was just a momentary interruption of service.

Yet, shortly after I delete all but one MX record, things start to work ok.