FAQ for system administrators

In the following, we have listed replies to the most frequently asked questions. If these do not answer your question, you can also directly contact our support agents.


Why is their a delay in delivering my emails?

Since email is an asynchronous medium, we and all other providers cannot guarantee prompt delivery. However, we do have a large team of specialists who work on ensuring trouble-free email correspondence.

Why are my emails being identified as spam?

The GMX spam filter systems comprise a number of different IP-based and content-based filter modules. Nevertheless, an email can be incorrectly identified as spam. Please send us the extended header for any email of this kind.

How can I ensure that my emails are not identified as spam?

Please observe our recommendations on sending emails.

My systems have just recovered from a malfunction. Why are my emails still being rejected?

When our systems detect that spam is being sent from specific servers, IP-based blocking of the compromised system becomes effective. Please use this contact form so that we can manually unblock your systems.

How can I get on the GMX whitelist?

GMX does not offer this service. Please observe our recommendations on sending emails. If you observe these recommendations, whitelisting is unnecessary.

Does GMX use greylisting?

In case of unmistakable characteristics that indicate a spamming server, we delay any emails sent from a specific IP address, or reject them completely. Please observe our recommendations on sending emails in this respect. If you observe these references, we can rule out delayed acceptance of your emails.

Why are connections between my server and the GMX systems being refused?

Please check if your email server's IP address is listed on an established RBL list. You can check this here. Please contact the list operator directly in such a case.

Additionally, check your server logfiles as of the first occurrence of any error.

Check whether you comply with the standards defined by the RFCs. This includes providing a syntactically correct sending address, the use of HELOs that return the IP address in a reverse lookup, and setting up a Reverse DNS entry (FQDN) for your email server's IP address.

Your systems may have been misused to send emails by unauthorised persons. Harden your systems against unauthorised use.

If you send newsletters or mass mails, check your delivery quota and remove any email addresses that no longer exist from your database. You must have the explicit permission of all recipients who you send emails to.

Please contact us to discuss the situation and/or unblock your server. Please send us relevant logfile entries and a description of the error that occurred including the error messages. Please use our contact form for this purpose.

Why are emails rendered differently at GMX that in an email program?

Active elements in an email, such as JavaScript, are disabled for security reasons when rendering emails in mailboxes. If this email is retrieved using an email program, the transmission is effected without any modification by GMX.

My question wasn't listed. How can I contact GMX?

If you have any further questions about sending emails to GMX, please use the contact form to contact us.

  1. 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.
  2. Indicates documents that describe the technical or organizational guidelines for the internet.
  3. 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.
  4. 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.