How to resolve this delivery failure problem

[rbby2003]

Emails from a@Adomain.com, sent to b@Bdomain.com, receive a MTA Response:4.4.1 delivery failure message after I changed doamin @Bdomain.com's IP address last Friday( that is 7 days ago), domain @Bdomain.com is hosted on a Windows Small Business Server 2003/Exchange server 2003 machine. After I changed the IP and MX record for @Bdomain.com, only @Adomain.com reported problems, and before the IP and MX record change for @Bdomain.com, there is no problem between @Adomain.com and @Bdomain.com, I mean emails sent between each other worked fine.

I tried to send email from other doamins to @Bdomain.com and NO problem. First I thought it could be a delay problem. But the TTL value for MX record and related A record was 1 day on @Bdomain.com before the change, and it is been 7 days since the change. This could not be a delay problem.

What can I do to resolve this delivery failure problem?

Any help will be appreciated.

 

[ShackDaddy]

Use nslookup to determine how @Adomain is coming up with the MX record that it is using to find @Bdomain. Where is @Adomain pointed to for DNS? Somehow it's using old information.

type 'nslookup'
type 'set type="MX"
type 'BDomain.com'

See what gets returned. Is it the old address, or the new one? If it's the new one, then the bad setting you have must be in your exchange server. Perhaps you configured something for Bdomain.com in ADomain.com's SMTP connector properties that is overriding proper DNS resolution.

ShackDaddy

 

[rbby2003]

ShackDaddy,
Thank you for your idea.
you are right. Somehow @Adomain.com is using my @Bdomain.com's old IP address to send emails to my @Bdomain.com. I don't understand how this happened. Since all the Cached DNS entries about @Bdomain.com should be wiped out automatically on the Internet after they expire, and the time should be determined by my DNS setup for @Bdomain.com. But it's been 6 days since the IP change for @Bdomain.com, and old DNS entries for @Bdomain.com is just 1 day. I have full control over @Bdomain.com' DNS, name server and Exchange. I did not do any manual setup for @Adomain.com on my Exchange server @Bdomain. Until now, all other domains work fine with my @Bdomain.com

I will ask the person who is taking care of @Adomain.com to check it as you suggested.

 

[ShackDaddy]

You know you can wipe out all cached entries on ADomain.com by doing an 'ipconfig /flushdns' at the command line on that DNS/mail server.

Personally, I don't think that cached entries is the problem. Something probably got hardcoded, perhaps they set up an extra zone for BDomain.com on the ADomain.com's DNS server, and the mailserver there is checking that zone file instead of querying BDomain.com's server. That's not uncommon among partner companies, although it's not a great practice.

ShackDaddy