Domino Server causes intermittent email bouncing
On a Domino Server to 8.5FP1
After upgrading a Domino Server to 8.5FP1 we noticed intermittent email bouncing even though the emails were correctly delivered to the email server. The server response was:
451 Unable to complete command, DNS not available or timed out
This message is misleading. What it really means that Domino wasn’t able to verify the sender domain’s RDNS (reverse DNS) entry.
Disabling Reverse DNS Check
If your Domino infrastructure already has a security mail gateway, then this extra protection on the Domino server isn’t needed and disabling it will speed up the SMTP operations of the Domino Server. Here are steps on how to turd this feature off.
Steps to turn off rDNS checking on the Domino Server
- Make sure you already have a Configuration Settings document for the server(s) to be configured.
- From the Domino Administrator, click the Configuration tab and expand the Messaging section.
- Select the Configuration Settings document for the mail server or servers you want to restrict mail on, and click Edit Configuration.
- Click the Router/SMTP – Restrictions and Controls – SMTP Inbound Controls tab.
- Set the field “Verify sender’s domain in DNS” in the Inbound Sender Controls section do “Disabled,” and then click Save & Close
More information on Domino Server SPAM prevention
- Restricting who can send Internet mail to your users
- Using ‘Verify Sender’s Domain’ in DNS can affect performance of SMTP task