Hello everyone I am using Exchange Server 2007 , Recently we have switched over to another ISP, so the public IP has been changed. i am not receiving mails from few domains , since their mails are hitting the old public IP not the new Public IP. They are getting this error: A communication failure occurred during the delivery of this message. Please to resend the message later. If the problem continues, contact your helpdesk. The following organization rejected your message: mail.abcdef.com (192.168.1.1). 192.168.1.1 is old public IP and our new public IP say 172.168.1.1. How to troubleshoot this problem.is this the problem at my end or their end because i am getting mails from all other domains only from few domains i am not getting emails. please guide me how to troubleshoot

Hi, If the MX records and A-records are updated to the new IP then there should be a max of 24 hours for the other servers to hit the correct IP. It all depends on the TTL set on the records in the first place. In a few cases I have seen a delay up to 48 hours. A way to work around it could be to contact the few domains that are having the issue and force them to update the A-record. /martinExchange is a passion not just a collaboration software.

Yup, external DNS - MX record would be my guess. J

Yup, external DNS - MX record would be my guess. J

Since my DNS is with ISP so i have to lookup for A Record and MX record . is anything else which i am missing.

Hello, I have checked with our ISP the entry is correct but at our older ISP there was a reverse lookup entry pointing to my server which was causing trouble. so i have asked old isp to remove this entry and it is almost 10 hours and still i am facing the same issue. i was told it may take 24 hours to propagate this entry. To be at the safer side i want to cross check at our ISP for the entries for our exchange server so please guide me. say my domain: abc.com 192.168.1.1(public IP) and my exchange server : mail.abc.com 192.168.1.2 (Public IP) Entries at The ISP A record with IP 192.168.1.2 MX record with IP 192.168.1.2 Reverse lookup record with IP 192.168.1.2 Autodiscover record with IP 192.168.1.2 Entries at my End(My Server) Autodiscover record pointing to ip 192.168.1.2 Anything else i am missing please do guide me.

Hello, I have checked with our ISP the entry is correct but at our older ISP there was a reverse lookup entry pointing to my server which was causing trouble. so i have asked old isp to remove this entry and it is almost 10 hours and still i am facing the same issue. i was told it may take 24 hours to propagate this entry. To be at the safer side i want to cross check at our ISP for the entries for our exchange server so please guide me. say my domain: abc.com 192.168.1.1(public IP) and my exchange server : mail.abc.com 192.168.1.2 (Public IP) Entries at The ISP A record with IP 192.168.1.2 MX record with IP 192.168.1.2 Reverse lookup record with IP 192.168.1.2 Autodiscover record with IP 192.168.1.2 Entries at my End(My Server) Autodiscover record pointing to ip 192.168.1.2 Anything else i am missing please do guide me.

On Wed, 16 Nov 2011 15:31:06 +0000, Risingflight wrote: >Hello, I have checked with our ISP the entry is correct but at our older ISP there was a reverse lookup entry pointing to my server which was causing trouble. If you changed IP addresses I don't see how a PTR record for your old IP address would be causing you problems, especially with _receiving_ messages. >so i have asked old isp to remove this entry and it is almost 10 hours and still i am facing the same issue. i was told it may take 24 hours to propagate this entry. To be at the safer side i want to cross check at our ISP for the entries for our exchange server so please guide me. say my domain: abc.com 192.168.1.1(public IP) and my exchange server : mail.abc.com 192.168.1.2 (Public IP) Entries at The ISP A record with IP 192.168.1.2 MX record with IP 192.168.1.2 Reverse lookup record with IP 192.168.1.2 Autodiscover record with IP 192.168.1.2 Entries at my End(My Server) Autodiscover record pointing to ip 192.168.1.2 Anything else i am missing please do guide me. You have no control over how other MTAs (or DNS) may, or may not, have cached the results of a DNS query. What was the TTL value on your old MX and A records? Has that TTL expired since you changed IP addresses? Even if the TTL *has* expired you may find some MTAs (or DNS) may still have your old information in their cached results. --- Rich Matheisen MCSE+I, Exchange MVP --- Rich Matheisen MCSE+I, Exchange MVP

I went through this twice already. Ensure you have reverse DNS record for your new IP. Please see this: http://joserebellon.wordpress.com/. You need to contact your ISP for this.