I am stumped as to why I cannot send email to this one particular domain; our sister company (springlinecorp.com). Mail to that domain is stuck in the queue of my CAS/HUB (EX2010/SP1/MR2) server. For that specific domain I'm getting the following error in the queue viewer: 451 4.4.0 Primary target IP address responded with: "." Attempted failover etc, etc, etc. I used NSLOOKUP to query the MX server that was being used and it came back with two entries for that domain: springlinecorp-com.mail.eo.outlook.com (65.55.88.22) springlinecorp-com.mail.eo.outlook.com (216.32.180.22) If you query springlinecorp.com at, for example, MX Toolbox you'll get the first entry (springlinecorp-com.mail.eo.outlook.com/65.55.88.22) as the correct and only entry. I'm not sure where the second one came from. Here's what I've done to try to correct the situation: 1) Cleared cache on DNS server/domain controllers through the DNS mmc and using ipconfig /flushdns (as Administrator). 2) Ran ipconfig /flushdns (as Administrator) on my CAS/HUB server. 3) Went into the forwarders tab in my DNS config and tried a different, external, DNS server. I still continue to get the same results. Is there something I'm missing? We need to be able to send correspondence to our sister company. We can receive their email without any problems but we cannot send to them. We are having no problems whatsoever sending email to anyone else. Many thanks in advance for your time and help with this issue.

When I do an nslookup from here, I got both of the entries that you have posted, so it would appear to be correct. Have you actually tried to telnet to the IP address on port 25 to see what the response is? Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

On Fri, 19 Aug 2011 16:37:13 +0000, NTElvin wrote: > > >I am stumped as to why I cannot send email to this one particular domain; our sister company (springlinecorp.com). Mail to that domain is stuck in the queue of my CAS/HUB (EX2010/SP1/MR2) server. > >For that specific domain I'm getting the following error in the queue viewer: > >451 4.4.0 Primary target IP address responded with: "." Attempted failover etc, etc, etc. > >I used NSLOOKUP to query the MX server that was being used and it came back with two entries for that domain: > >springlinecorp-com.mail.eo.outlook.com (65.55.88.22) springlinecorp-com.mail.eo.outlook.com (216.32.180.22) > >If you query springlinecorp.com at, for example, MX Toolbox you'll get the first entry (springlinecorp-com.mail.eo.outlook.com/65.55.88.22) as the correct and only entry. I'm not sure where the second one came from. Looks like the other company is using BPOS, Office 365, or just having its e-mail filtered by FOPE. If you're not getting a 220 SMTP banner when you connect to the machines then you may have a connectivity problem. 220 TX2EHSMHS045.bigfish.com Microsoft ESMTP MAIL Service ready at Sat, 20 Aug 2011 03:19:17 +0000 >Here's what I've done to try to correct the situation: > >1) Cleared cache on DNS server/domain controllers through the DNS mmc and using ipconfig /flushdns (as Administrator). 2) Ran ipconfig /flushdns (as Administrator) on my CAS/HUB server. 3) Went into the forwarders tab in my DNS config and tried a different, external, DNS server. > >I still continue to get the same results. Is there something I'm missing? We need to be able to send correspondence to our sister company. We can receive their email without any problems but we cannot send to them. We are having no problems whatsoever sending email to anyone else. They should be able to add your IP address to FOPE's white list for their domain (if they're using the full-on FOPE and not just the one that assumes your e-mail is being filtered by the on-premises Exchange servers). --- Rich Matheisen MCSE+I, Exchange MVP --- Rich Matheisen MCSE+I, Exchange MVP

On Fri, 19 Aug 2011 16:37:13 +0000, NTElvin wrote: > > >I am stumped as to why I cannot send email to this one particular domain; our sister company (springlinecorp.com). Mail to that domain is stuck in the queue of my CAS/HUB (EX2010/SP1/MR2) server. > >For that specific domain I'm getting the following error in the queue viewer: > >451 4.4.0 Primary target IP address responded with: "." Attempted failover etc, etc, etc. > >I used NSLOOKUP to query the MX server that was being used and it came back with two entries for that domain: > >springlinecorp-com.mail.eo.outlook.com (65.55.88.22) springlinecorp-com.mail.eo.outlook.com (216.32.180.22) > >If you query springlinecorp.com at, for example, MX Toolbox you'll get the first entry (springlinecorp-com.mail.eo.outlook.com/65.55.88.22) as the correct and only entry. I'm not sure where the second one came from. Looks like the other company is using BPOS, Office 365, or just having its e-mail filtered by FOPE. If you're not getting a 220 SMTP banner when you connect to the machines then you may have a connectivity problem. 220 TX2EHSMHS045.bigfish.com Microsoft ESMTP MAIL Service ready at Sat, 20 Aug 2011 03:19:17 +0000 >Here's what I've done to try to correct the situation: > >1) Cleared cache on DNS server/domain controllers through the DNS mmc and using ipconfig /flushdns (as Administrator). 2) Ran ipconfig /flushdns (as Administrator) on my CAS/HUB server. 3) Went into the forwarders tab in my DNS config and tried a different, external, DNS server. > >I still continue to get the same results. Is there something I'm missing? We need to be able to send correspondence to our sister company. We can receive their email without any problems but we cannot send to them. We are having no problems whatsoever sending email to anyone else. They should be able to add your IP address to FOPE's white list for their domain (if they're using the full-on FOPE and not just the one that assumes your e-mail is being filtered by the on-premises Exchange servers). --- Rich Matheisen MCSE+I, Exchange MVP --- Rich Matheisen MCSE+I, Exchange MVP 220 VA3EHSMHS021.bigfish.com Microsoft ESMTP MAIL Service ready at Sat, 20 Aug 2011 07:42:12 +0000 OK - 216.32.180.22 resolves to mail.global.frontbridge.com Warning - Reverse DNS does not match SMTP Banner 0 seconds - Good on Connection time Not an open relay. 0.250 seconds - Good on Transaction time It should be working Regards Abhinav "Abhi" "Exchange Specialist" ------------- Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

UPDATE: We tried telnetting into the remote server and we got a response, so we figured it was something on our end (we our sister company hosted on MS 365, we host our own Exchange 2010 servers). We decided to stop/restart the Exchange Transport Service and... BINGO, we're able to email them now. Something was definitely "stuck" somewhere but thankfully the problem us now resolved. Special thanks to all that responded to our my inquiry. If you ever visit NYC drinks on me! Cheers!