Email policy

GMX considers it its responsibility to provide its users with trustworthy and secure service. We therefore place the highest priority on the careful evaluation of incoming emails as well as on taking action against unsolicited messages.

To ensure that you do not experience a connection issue or a sending issue when trying to send emails to GMX customers, please adhere to the following policies and make sure your mail server's configuration is adjusted accordingly.

Technical Guidelines:



  1. The email header contains technical information on the process of sending an email. Most email programs and webmail interfaces hide the email header. In contrast to this, the email body (the text itself) is typically displaced. The body can be pure text or comprise multiple elements such as text and attachments.
  2. The HELO command is part of the SMTP protocol used for email delivery. With the help of this command, the email exchange between two servers gets initiated as the sending server transmits its full domain name. Analogous to that, a server indicates by means of the EHLO command that the extended SMTP protocol version (ESMTP) should be used.
  3. A Reverse DNS entry or FQDN (Fully Qualified Domain Name or PTR-RR) is the unique name of an internet host. The FQDN can be used to discover the host's IP address. The Reverse DNS entry should be used as the HELO when sending emails. You can find detailed information in the Digital Guide from IONOS.
  4. SPF (Sender Policy Framework) is a technology designed to make it more difficult to spoof sender addresses. It ascertains the IP addresses from which emails with a specific sender domain can be sent (or from which IP addresses mails may not be sent). To allow this to happen a TXT type (or SPF type if it exists) resource record is created in the DNS zone; it lists all the authorised IP addresses used as sending addresses in the domain. For more information on setting up an SPF record, see the website.
    When an email is redirected, a receiving system that validates email reception against an SPF entry is unable to validate the sender's identity. Forwarding servers should use SRS to encapsulate the sending address in an envelope to prevent SPF validation returning incorrect results. For more information on SRS refer to the site.
  5. An RBL list collects IP addresses. The list can be used to decide before establishing a connection if specific email senders are allowed to deliver to the receiving system, and to evaluate the spam probability with which emails are tagged. There are various types of lists of this kind. Some include IP addresses from which the owner is not prepared to receive and to which they are not prepared to send emails. Other lists include IP addresses which are known to be responsible for sending spam mail.