Check that your server is not on any RBL list (real time black hole list). Alternately set up a smart host to send through a provider they don't block (like gmail/google apps for domains). You can test manually using telnet. First get their mail exchange records: nslookup -query=MX comcast.com Server: x.x.x.x Address: y.y.y.y#53 Non-authoritative answer: comcast.com mail exchanger = 5 mx1.comcast.com. comcast.com mail exchanger = 5 mx2.comcast.com. comcast.com mail exchanger = 5 mx3.comcast.com. comcast.com mail exchanger = 5 mx4.comcast.com. Authoritative answers can be found from: comcast.com nameserver = dns101.comcast.net. comcast.com nameserver = dns102.comcast.net. comcast.com nameserver = dns103.comcast.net. comcast.com nameserver = dns104.comcast.net. comcast.com nameserver = dns105.comcast.net. mx1.comcast.com internet address = 76.96.32.247 mx2.comcast.com internet address = 76.96.32.252 mx3.comcast.com internet address = 69.241.43.117 mx4.comcast.com internet address = 69.241.43.118 telnet 76.96.32.24 25 helo mail from:< user>@ rcpt to:@c omcast.com This is a test email . On Wed, Nov 21, 2012 at 4:50 PM, keith smith wrote: > > Hi, > > > One of the Vhost on a server I run is a shopping cart. We have been > experiencing bounced emails when sending to Comcast. We do not have this > problem with any other ISP. > > > These emails are sent directly from the box, such as the order > confirmation email. > > > The problem started when we upgraded from CentOS 5.x to CentOS 6.x. I > wonder if anyone else has experience this problem. > > > The failure message: > > > Hi. This is the qmail-send program at [boxes fully qualified domain > name]. > > I'm afraid I wasn't able to deliver your message to the following > addresses. > > This is a permanent error; I've given up. Sorry it didn't work out. > > > > [ customers email address]: > > CNAME lookup failed temporarily. (#4.4.3) I'm not going to try again; > > this message has been in the queue too long. > > Only happens when emails are sent to Comcast directly from the server - > order confirmation and shipping confirmation. > > I've search for a solution and read this can be corrected by setting the > DISABLE_CNAME_LOOKUP in qmail-remote. Something about a buffer being too > small?? > > > Is this true or could it be another issue? > > > Thank you for your feedback! > > > Keith > > > > ------------------------ > Keith Smith > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss >