Frequently Asked Questions about the DNS requirements from Cantv.net, to users of its email platform. This document is most relevant to senders whose email has been rejected with errors related to the DNS or its configuration.
The contents of this question list are revised whenever new questions or doubts are identified in the communications with our users. Please carefully review the questions and answers that might be related with your doubts, as we've made an important effort to provide ample and complete answers.
If you do not find the answer you need in this site, please let us know by using the links at the end of each page.
- Why is email rejected with a reference to this page?
- What is an inverse? What is an IN PTR record?
- Who must correct this problem so that email can flow? How long does this take?
- This situation is not a problem or error of Cantv.net, but of the ISP providing access or messaging services
- Exceptions or special considerations
- Warnings that Cantv.net has made to other ISPs about this requisite
Why is email rejected with a reference to this page?
An important fraction of the bulk and unsolicited messages directed to the mailboxes of our users, as well as virus and other forms of malicious content, come from equipment connected to the Internet without the required configuration. The relevant technical standards establish that each device connected to the Internet should have an inverse or IN PTR record.
By refusing to accept email coming from incorrectly configured equipment, we immediately and significantly reduced the amount of spam and other forms of unsolicited email that our users and subscribers have to cope with, improving the experience we offer with regard to our Internet access services. Likewise, this measure has little impact, as most ISPs already know how to properly configure their networks.
Since August 2003, Cantv.net has published a set of technical requirements for the use of its email platform, including the configuration of inverses. The requisite of maintaining correct DNS information in order to use our email platform begun to be enforced in October 2004, 14 months later.
<<What is an inverse? What is an IN PTR record?
An inverse in this context, refers to an association or register that allows the cannonical name of a network resource to be obtained. Is is assigned by the network operator to a given device connected to the Internet, to each IP address under his or her responsibility. This is also referred to as an IN PTR record in DNS parlance.
This information allows the quick and automatic identification of the entity responsible for the operation of the given device within the Internet and is a well known operational requisite.
<<Who must correct this problem so that email can flow? How long does this take?
Usually, this problem must be corrected by whomever is responsible to operate your network or your email platform, which most times is your ISP.
Technically, the fix is very simple. We offer technical help on this topic at http://abuso.cantv.net/docs/isp-tips. The time it takes for the responsible party to correct the problem, depends entirely in the specifics of each situation and in any case, this escapes the knowledge or responsibility of Cantv.net
<<This situation is not a problem or error of Cantv.net, but of the ISP providing access or messaging services
The implementation of this protection scheme for our users, is a completely intentional decision in the part of Cantv.net. We understand that in some cases, some legitimate messages might be blocked.
We do not consider this situation to be an error, oversight or problem of Cantv.net as we've made more than reasonable efforts to notify those system administrators that might have been affected by this, as explained in other parts of this document. Additionally, RFCs 1123, 1034 and 1035 -which date back to the 80s and which define how to technically operate on the Internet- specify that each device connected to the Internet must be configured with a corresponding inverse.
<<Exceptions or special considerations
In special cases, Cantv.net may make temporary exceptions to respond to cases that at its sole discretion, merit this. The requesting entity must strictly abide with the rest of our technical requirements for use of our email platform and present all the justifications and requisites required by Cantv.net.
Cantv.net is under no obligation to make exceptions to its technical conditions, among which the correct DNS configuration is prominently included.
<<Warnings that Cantv.net has made to other ISPs about this requisite
Starting on May 2004, Cantv.net placed the following technical message in its email platform:
$ telnet mail.cantv.net 25 Trying 200.44.32.43... Connected to mail.cantv.net. Escape character is '^]'. 220-rs25s12.datacenter.cha.cantv.net ESMTP Exchange Server 2.236/2.0 220-Vea http://www.cantv.net/seguridad/email para terminos y condiciones 220-de uso de este servicio, especialmente en cuanto a los requerimientos 220-tecnicos necesarios para que Cantv.net acepte sus mensajes 220 Mon, 6 Sep 2004 15:35:50 -0400
This text refers the reader to the URL where our technical conditions are explained, including the requirement to maintain proper DNS configuration for machines connecting to our email platform.
As a complement, in September 2003, we identified all devices without inverses that were connecting to our email platform. Afterwards, we notified the administrators of said equipment about the problem using email. In these messages we notified about the problem with more than enough time for action before the enforcement of this defense mechanism.
This process gave the network operators close to one month to take the simple corrective actions that were required to correct the configuration of their servers.
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