I’ve got an issue that is making me pull my hair out, and I’m hoping someone can give me a lead.
I am running an Exchange 5.5 server and a my own DNS SOA, using my ISP’s DNS servers as backup. The system has been solid since September when it wasfirst put in.
Recently though, and for no apparent reason, I started receiving reports from people on the outside saying that they were sometimes not able to get e-mail through to my domain, and that they were receving bounce-backs.
The bouncebacks indicate a “host not found” error for my Exchange server’s FQDN. This would seem to imply that it’s not a connectivity or a resolution issue, but one where the Exchange server, for some reason, is not responding (or not responding fast enough).
It is difficult to know exactly when this problem is occuring or how long it lasts when it does, but the evidence thus far would indicate that it does not appear to happen very often (maybe once a day) and when it occurs, it does not last for more than a second or two. In almost every case, simply re-sending the message a second time gets it through without incident.
This fact, however, makes the issue maddeningly difficult to track down. I have checked my DNS server, my Exchange server, and checked with the ISP who is providing us with our connectivity (a dedicated T1 line), and can find no evidence of a problem anywhere, but yet the issue persists, albeit on an irregular and upredictable basis.
Has anyone out there experience this phenomenon, or something similar? If so, I would love to get some ideas on how to nail this down.
Thanks in advance.
Joe
