Outbound SMTP mail issue

HCL Domino Domino Forum
1

We are experiencing a weird outbound SMTP mail issue.

Some domains we send to intermittently get “The server is not a known TCPIP host.” and rejected due to DNS domain not found errors. The domain name in question does exist and some messages get through.

This is all from the same Domino SMTP server.

The Outbound SMTP server is Domino 6.5.1 - and most mail (99% +) is delivered fine without issues, only certain domains seem to have this problem.

If I do a “te router sh” and I see a message to this domain stuck (on several retries), then restart the router (not SMTP) the message(s) will go through right away.

These issues only seem to start if the router has been up for a while.

It seems that after the initial failure it will not find the host unless the router is restarted.

Is this a Domino issue, a DNS issue or what?

Any comments or suggestions will be appreciated.

2

Subject: Outbound SMTP mail issue

I had a similar problem, but it was when we changed domain names and some systems were not able to send to us. In my case it was a DNS issue, my DNS. In your case it could be your DNS or the DNS of the system your messages are rejected. Since e-mail messages are sent with domain names and not IP addresses they must be resolved into IP addresses in order to be properly routed. If your DNS can’t get the proper IP address from their DNS then Domino can’t properly route the e-mail. Another possiblity is your router table may have a problem with properly refreshing itself, when it gets a bad DNS resolution it can’t overwrite itself when a proper resolution is found until you restart it.