I recently started using CloudFlare and am having a few teething problems.
Our domain is netlanguages.com and while we have a lot of sub-domains listen, we are currently only trialling a few of the servers through the CloudFlare CDN (for example, www.netlanguages.com is enabled for CDN, netlanguages.com is not). The actual CDN service seems
to be reliable, but the problem that we are having is with DNS, and specifically with mail delivery.
The background is that we have contact forms on our web site which use PHP mail()
to send the details
to end-users' email addresses, with the "from" address of the messages being
[email protected] which is a valid address on our mail server. Most of the mails are arriving correctly, but a few specific people are not receiving them. The webserver uses qmail
to deliver the messages, and the qmail log files show us some of the errors that the receiving mail servers return when they reject the mail delivery attempt. Two examples:
Connected
to 94.100.176.20 but sender was rejected./Remote host said: 421 DNS problem (interdominios.netlanguages.com). Try again later
Connected
to 213.186.33.29 but sender was rejected./Remote host said: 451 DNS temporary failure (#4.3.0)
From what I can tell, the receiving SMTP server is doing a DNS lookup of some description on either the host of the "from" email address (netlanguages.com) or the server name given in the EHLO command of the SMTP conversation (in the first example above, interdominios.netlanguages.com), both of which should resolve
to non-CloudFlare IP addresses.
I've read that the CloudFlare DNS service is very reliable and fast but both of the problems above seem
to point
to a problem with
remote servers unable
to do DNS lookups.
I should also point out that we changed our DNS
to CloudFlare on 6th Feb, and since then started experiencing these mail delivery problems. On 22nd Feb we moved our DNS away from CloudFlare
to see if the issues were related
to CloudFlare and after a few hours delivery began
to work. Then on 26th Feb I moved the DNS back
to CloudFlare again and delivery problems started again. The issues definitely seems
to be related
to DNS, but I don't know if it's a configuration issue, or something else.
Finally, I should say that our two DNS MX records point
to non-CDN A record IP addresses, interdominios.netlanguages.com (the web and qmail server) also points
to a non-CDN A record IP address.
Does anyone know what the problem could be here? Any light you can shed on this will be most appreciated.
Many thanks,
Andy
