Exchange 2003 not accepting email from some users.

[tmcdonald61]

Hello. I have a problem with email to a partner that we have been receiving stuff to for years but suddenly all their email is bounced back as non-deliverable. I have been talking with them and they say nothing has changed on their end. The only chang on our end is removing a frontend server and using Postini. It's only email from them to us that gets rejected (tested with other outside email and it works fine) and we are able to send to them. Has anyone run into a similar situation before?

We have microsoft exchange 2003 (latest SP and patches).

Errors they receive are as follows:

The destination server for this recipient could not be found in Domain Name Service (DNS). Please verify the email address and retry. If that fails, contact your administrator.
<ubgexchange.unitybuilders.com #5.4.0>

Could not deliver the message in the time limit specified. Please retry or contact your administrator.
<ubgexchange.unitybuilders.com #4.4.7>

The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator.
<ubgexchange.unitybuilders.com #4.0.0 smtp;417 DNS lookup failure: unitybuilders.com. Try again later.

Any ideas?
tmcdonald61

 

[gurner]

what records do they get if they try an NSLOOKUP from their mail server?

Start>Run>'CMD' [OK]

type 'nslookup' [enter]

set type MX [enter]
domainame.com [enter]

if it displays an IP is it correct?

Probably is

if there is a Host name is this correct?

how do you recieve mail? does an ISP forward to and from you or do you have a more direct method where someone sending mail connects to your mail server?

are they connecting to the correct machine? (this is where the nslookup comes in)

Also, in either case they could try Telnetting on port 25 (from their mail server) to either your ISP (in the case of forwarding) or to your mail server and try the manual method via a command line.

more on this later

Gurner

http://www.harryontheboat.co.uk

 

[NetworkDOC]

It sure sounds like DNS.

Go to DNSREPORT.com run a test on you and them. See specifically if you/them have reverse DNS configured corectly.

Other things, if you are using M/S 2003 for DNS check into the EDNS0 Issue You may need to add this to the 2003 DNS server.

dnscmd ServerName /Config /EnableEDnsProbes 0

Other issues are with a PIX and DNS.

THe no fixup DNS command will resolve this if that is teh case.