It's probably backscatter: http://www.postfix.org/BACKSCATTER_README.html
-----Original Message----- From: owner-postfix-us...@postfix.org [mailto:owner-postfix-us...@postfix.org] On Behalf Of James B. Byrne Sent: Wednesday, November 7, 2018 11:06 AM To: postfix-us...@cloud9.net Subject: Name Service error but resolver is working On our IMAP service host I am seeing messages in the mailq similar to the following: 50DFB12B2F7 7501 Tue Nov 6 17:22:42 MAILER-DAEMON (delivery temporarily suspended: Host or domain name not found. Name service error for name=mx31.harte-lyne.ca type=MX: Host not found, try again) Postfix on the IMAP host is configured to route outgoing mail through MX31. And mail is flowing in and out of the IMAP system. Most things are being delivered. But a few messages are stuck in the mail queue with this error and I cannot figure out what the problem with them is. I have confirmed that the DNS resolver on both the IMAP host and MX31 are working. I can ping from the IMAP host to MX31. On the IMAP host I can use swaks to successfully send mail via the localhost. On the IMAP host I can also use swaks to successfully send mail via MX31. The test messages both arrived in the destination mailbox on the IMAP host. I do not understand what the DNS issue is, but I cannot flush messages with this error. -- *** e-Mail is NOT a SECURE channel *** Do NOT transmit sensitive data via e-Mail Do NOT open attachments nor follow links sent by e-Mail James B. Byrne mailto:byrn...@harte-lyne.ca Harte & Lyne Limited http://www.harte-lyne.ca 9 Brockley Drive vox: +1 905 561 1241 Hamilton, Ontario fax: +1 905 561 0757 Canada L8E 3C3
