Our company has been having trouble sending to a single domain. All our mail gets bounced back. At first I figured it must be their server since everything else works but they of course said it couldn't be. They can send to us, we cannot reply. We have no issues with email going to any other server. Our Exchange is setup to use a SonicWall server for all incoming and outgoing mail. We are using the ISP's DNS as external DNS (we have a odd internal system and our DNS gets forwarded to another company's DNS). When we send a email to the company we are having trouble with we get this back: The following recipient(s) could not be reached: (namechanged)@eaglegolf.com on 9/2/2010 3:32 AM 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. <SonicWall.OurDomain.Local #4.4.1> So from the error message I thought that it was a DNS issue BUT based on the 4.4.1 its not. I tried a nslookup to test the resolution: C:\Documents and Settings\Administrator>nslookup Default Server: EMail.OurDomain.Local Address: 10.*.*.* > set type=mx > eaglegolf.com Server: cleemail1.whg.local Address: 10.*.*.* Non-authoritative answer: eaglegolf.com MX preference = 10, mail exchanger = mail.eaglegolf.com mail.eaglegolf.com internet address = 12.181.144.250 > So checking the mx record for their domain does resolve just fine. So based on the 4.4.1 being a non responsive server I would think they are slow to respond. But if I send to their domain with another email service (Hotmail, GMail, etc) it goes through instantly. What could it be? I have talked to their IT people and they just keep saying it has to be something with my system. I don't see how that's possible....it's acting like we are blacklisted on their server so it's ignoring our IP and requests. Does this make sense?

Hi, Here can be two issue for mail flow : 1: Check whether your domain is having vallid PTR record (I understand you are able to send to other) 2: Check whetehr you are server does not come under RBL databse (You must get this info IN NDR) 3: Check with remote domain admin why they are not accepting message for your SMTP IP or domain name 4: If possible then try to change IP of Sonica wall (NAT IP External IP) whther remote domain able to accept message from other IP (Your external IP ) Hope above info will help you to troubleshoot !!!Anil

Anil, Our PTR records are good, havn't changed in 4+ years. Also I checked MXToolbox.com and everything looks good there, SMTP test works, Blacklist comes up with all green. Nothing appears wrong. I also checked their domain and it's clean too. I'm really thinking they have us black listed but I can't get their IT people to confirm it. Here's why I say that. I plgged my cell phone into my laptop and used it for internet access. I then pinged their mail server and got valid replies. I then telnet'd into their mail server ("telnet mail.eaglegolf.com 25") to see what reply I get: 554-mail.eaglegolf.com 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means. Connection to host lost. So that looks valid. I logged into my SonicWall box and tried pinging the same domain. The domain resolved BUT the pings all time out. I then tried to telnet into their mail server from my SonicWall box. It connects and then just sits on a blank screen and never changes (I left it sit there for 15 minutes). So is there anything else I can do?

Well it's now working. I emailed there It people all the things I did to test the connection including the fact that the telnet into their mail server was hanging and not replying back. Magically (sic) after I sent those emails there mail server started responding to my telnet correctly. They said they didn't change anything, which I guess is possible but not likely....